UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 6-K REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TO RULE 13a-16 OR 15d-16 UNDER THE SECURITIES EXCHANGE ACT OF 1934 For the month of January 2004 SPIRENT plc _____________________________________________________________________ (Translation of registrant's name into English) Spirent House, Crawley Business Quarter, Fleming Way, Crawley, West Sussex RH10 9QL, UK. _____________________________________________________________________ (Address of principal executive offices) Indicate by check mark whether the registrant files or will file annual reports under cover Form 20-F or Form 40-F. Form 20-F X Form 40-F..... Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934. Yes ..... No X If "Yes" is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b): 82- ________ BLOCK LISTING SIX MONTHLY RETURN To: Listing Applications UK Listing Authority Old Broad Street London EC2N 1HP (020 7588 6057) Name of company: SPIRENT PLC Name of scheme: CAW AMENDED AND RESTATED STOCK OPTION PLAN Period of return: From: 01 JULY 2003 To: 31 DECEMBER 2003 Number and class of share(s) (amount of Stock/debt 1,205,164 ORDINARY SHARES OF 3 1/3p EACH security) not issued under scheme at end of the last period: Number of shares issued/allotted under scheme during 40,438 ORDINARY SHARES period: Balance under scheme not yet issued/allotted at end 1,164,726 ORDINARY SHARES of period: Number and class of share(s) (amount of stock/debt 1,300,000 ORDINARY SHARES OF 3 1/3p EACH securities) originally listed and the date of admission: DATED 15 AUGUST 2002 115,394 ORDINARY SHARES OF 3 1/3P EACH DATED 28 AUGUST 2002 Please confirm total number of shares in issue at the end of the period in order for us to update our records 944,031,413 Contact for queries: Address: Spirent plc Name: Michael Anscombe Spirent House Telephone: 01293 767676 Crawley Business Quarter Fleming Way Crawley, RH10 9QL Person making return Name: Michael Anscombe Position: Assistant Company Secretary Signature: BLOCK LISTING SIX MONTHLY RETURN To: Listing Applications UK Listing Authority Old Broad Street London EC2N 1HP (020 7588 6057) ALL FIGURES HAVE BEEN REVISED FOR THE 3:1 SHARE SPLIT ON 11 MAY 2000 Name of company: SPIRENT PLC Name of scheme: SPIRENT EXECUTIVE SHARE OPTION SCHEME Period of return: From: 01 JULY 2003 To: 31 DECEMBER 2003 Number and class of share(s) (amount of Stock/debt 1,587,494 ORDINARY SHARES OF 3 1/3p EACH security) not issued under scheme at end of the last period: Number of shares issued/allotted under scheme during 0 ORDINARY SHARES period: Balance under scheme not yet issued/allotted at end 1,587,494 ORDINARY SHARES of period: Number and class of share(s) (amount of stock/debt 3,000,000 ORDINARY SHARES OF 3 1/3p EACH DATED 29/ securities) originally listed and the date of 09/2000 admission: Please confirm total number of shares in issue at the end of the period in order for us to update our records 944,031,413 Contact for queries: Address: Spirent plc Name: Michael Anscombe Spirent House Telephone: 01293 767676 Crawley Business Quarter Fleming Way Crawley, RH10 9QL Person making return Name: Michael Anscombe Position: Assistant Company Secretary Signature: BLOCK LISTING SIX MONTHLY RETURN To: Listing Applications UK Listing Authority Old Broad Street London EC2N 1HP (020 7588 6057) Name of company: SPIRENT PLC Name of scheme: U.S. EMPLOYEE STOCK PURCHASE PLAN Period of return: From: 01 JULY 2003 To: 31 DECEMBER 2003 Number and class of share(s) (amount of Stock/debt 4,980,140 ORDINARY SHARES OF 3 1/3p EACH security) not issued under scheme at end of the last period: Number of shares issued/allotted under scheme 25,104 ORDINARY SHARES during period: Balance under scheme not yet issued/allotted at end 4,955,036 ORDINARY SHARES of period: Number and class of share(s) (amount of stock/debt 435,000 ORDINARY SHARES OF 3 1/3P EACH securities) originally listed and the date of admission: ADMITTED 5 JUNE 2001 3,500,000 ORDINARY SHARES OF 3 1/3p EACH ADMITTED 1 NOVEMBER 2001 7,000,000 ORDINARY SHARES OF 3 1/3P EACH ADMITTED 18 NOVEMBER 2002 Please confirm total number of shares in issue at the end of the period in order for us to update our records 944,031,413 Contact for queries: Address: Spirent plc Name: Michael Anscombe Spirent House Telephone: 01293 767676 Crawley Business Quarter RH10 9QL Person making return Name: Michael Anscombe Position: Assistant Company Secretary Signature: BLOCK LISTING SIX MONTHLY RETURN To: Listing Applications UK Listing Authority Old Broad Street London EC2N 1HP (020 7588 6057) Name of company: SPIRENT PLC Name of scheme: GLOBAL ALL EMPLOYEE SHARE PURCHASE PLAN Period of return: From: 01 JULY 2003 To: 31 DECEMBER 2003 Number and class of share(s) (amount of Stock/debt 700,052 ORDINARY SHARES OF 3 1/3p EACH security) not issued under scheme at end of the last period: Number of shares issued/allotted under scheme 0 ORDINARY SHARES during period: Balance under scheme not yet issued/allotted at end 700,052 ORDINARY SHARES of period: Number and class of share(s) (amount of stock/debt 1,000,000 ORDINARY SHARES OF 3 1/3p EACH DATED 18 securities) originally listed and the date of NOVEMBER 2002 admission: Please confirm total number of shares in issue at the end of the period in order for us to update our records 944,031,413 Contact for queries: Address: Spirent plc Name: Michael Anscombe Spirent House Telephone: 01293 767676 Crawley Business Quarter RH10 9QL Person making return Name: Michael Anscombe Position: Assistant Company Secretary Signature: BLOCK LISTING SIX MONTHLY RETURN To: Listing Applications UK Listing Authority Old Broad Street London EC2N 1HP (020 7588 6057) ALL FIGURES HAVE BEEN REVISED FOR THE 3:1 SHARE SPLIT ON 11 MAY 2000 Name of company: SPIRENT PLC Name of scheme: NETCOM AMENDED AND RESTATED STOCK OPTION PLAN Period of return: From: 01 JULY 2003 To: 31 DECEMBER 2003 Number and class of share(s) (amount of Stock/debt 6,666,672 ORDINARY SHARES OF 3 1/3p EACH security) not issued under scheme at end of the last period: Number of shares issued/allotted under scheme during 389,988 ORDINARY SHARES period: Balance under scheme not yet issued/allotted at end 6,276,684 ORDINARY SHARES of period: Number and class of share(s) (amount of stock/debt 3,291,399 ORDINARY SHARES OF 3 1/3p EACH DATED 03/ securities) originally listed and the date of 09/1999 admission: 1,739,130 ORDINARY SHARES OF 3 1/3p EACH DATED 8 JULY 2002 6,722,689 ORDINARY SHARES OF 3 1/3P EACH DATED 8 OCTOBER 2002 Please confirm total number of shares in issue at the end of the period in order for us to update our records 944,031,413 Contact for queries: Address: Spirent plc Name: Michael Anscombe Spirent House Telephone: 01293 767676 Crawley Business Quarter Fleming Way Crawley, RH10 9QL Person making return Name: Michael Anscombe Position: Assistant Company Secretary Signature: BLOCK LISTING SIX MONTHLY RETURN To: Listing Applications UK Listing Authority Old Broad Street London EC2N 1HP (020 7588 6057) Name of company: SPIRENT PLC Name of scheme: ZARAK AMENDED AND RESTATED STOCK OPTION PLAN Period of return: From: 01 JULY 2003 To: 31 DECEMBER 2003 Number and class of share(s) (amount of Stock/debt 2,690,996 ORDINARY SHARES OF 3 1/3p EACH security) not issued under scheme at end of the last period: Number of shares issued/allotted under scheme during 0 ORDINARY SHARES period: Balance under scheme not yet issued/allotted at end 2,690,996 ORDINARY SHARES of period: Number and class of share(s) (amount of stock/debt 3,895,474 ORDINARY SHARES OF 3 1/3p EACH securities) originally listed and the date of admission: DATED 14 NOVEMBER 2000 Please confirm total number of shares in issue at the end of the period in order for us to update our records 944,031,413 Contact for queries: Address: Spirent plc Name: Michael Anscombe Spirent House Telephone: 01293 767676 Crawley Business Quarter Fleming Way Crawley, RH10 9QL Person making return Name: Michael Anscombe Position: Assistant Company Secretary Signature: BLOCK LISTING SIX MONTHLY RETURN To: Listing Applications UK Listing Authority Old Broad Street London EC2N 1HP (020 7588 6057) Name of company: SPIRENT PLC Name of scheme: SPIRENT SAVINGS RELATED SHARE OPTION SCHEME Period of return: From: 01 JULY 2003 To: 31 DECEMBER 2003 Number and class of share(s) (amount of Stock/debt 0 ORDINARY SHARES OF 3 1/3p EACH security) not issued under scheme at end of the last period: Number of shares issued/allotted under scheme during 1,065 ORDINARY SHARES period: Balance under scheme not yet issued/allotted at end 198,935 ORDINARY SHARES of period: Number and class of share(s) (amount of stock/debt 200,000 ORDINARY SHARES OF 3 1/3p EACH securities) originally listed and the date of admission: DATED 31 DECEMBER 2003 Please confirm total number of shares in issue at the end of the period in order for us to update our records 944,031,413 Contact for queries: Address: Spirent plc Name: Michael Anscombe Spirent House Telephone: 01293 767676 Crawley Business Quarter Fleming Way Crawley, RH10 9QL Person making return Name: Michael Anscombe Position: Assistant Company Secretary Signature: BLOCK LISTING SIX MONTHLY RETURN To: Listing Applications UK Listing Authority Old Broad Street London EC2N 1HP (020 7588 6057) Name of company: SPIRENT PLC Name of scheme: SPIRENT STOCK OPTION PLAN Period of return: From: 01 JULY 2003 To: 31 DECEMBER 2003 Number and class of share(s) (amount of Stock/debt 0 ORDINARY SHARES OF 3 1/3p EACH security) not issued under scheme at end of the last period: Number of shares issued/allotted under scheme during 411,032 ORDINARY SHARES period: Balance under scheme not yet issued/allotted at end 7,013,601 ORDINARY SHARES of period: Number and class of share(s) (amount of stock/debt 3,720,930 ORDINARY SHARES OF 3 1/3p EACH securities) originally listed and the date of admission: DATED 1 OCTOBER 2003 3,703,703 ORDINARY SHARES OF 3 1/3p EACH DATED 2 OCTOBER 2003 Please confirm total number of shares in issue at the end of the period in order for us to update our records 944,031,413 Contact for queries: Address: Spirent plc Name: Michael Anscombe Spirent House Telephone: 01293 767676 Crawley Business Quarter Fleming Way Crawley, RH10 9QL Person making return Name: Michael Anscombe Position: Assistant Company Secretary Signature: Signatures Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized. ______LUKE THOMAS______ (Registrant) Date _12 January 2004 By ____/s/ Luke Thomas____ (Signature)*