Crawley, UK -- (MARKET WIRE) -- December 28, 2006 --

                           SPIRENT COMMUNICATIONS PLC


London, UK - 28 December 2006: Spirent Communications plc ("the Company") (LSE: SPT; NYSE: SPM), a leading technology communications company would like to notify the market in compliance with the Transparency Directive's transitional provision 6, of the following information as at 28 December 2006:

The Company's issued share capital consists of 975,851,486 ordinary shares of 3 & 1/3 pence with voting rights. The Company holds 90,251,487 ordinary shares in Treasury, and the Company is not permitted to exercise voting rights in respect of those ordinary shares. Therefore, the total number of voting rights in the Company is 885,599,999.

The above figure (885,599,999) may be used by shareholders as the denominator for the calculations by which they will determine if they are required to notify their interest in, or a change to their interest in, the Company under the Financial Services Authority's Disclosure and Transparency Rules.

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  Michael Anscombe      Deputy Company Secretary        +44 (0)1273 767676

About Spirent Communications plc

Spirent Communications plc is a leading communications technology company focused on delivering innovative systems and services to meet the needs of customers worldwide. We are a global provider of performance analysis and service assurance solutions that enable the development and deployment of next-generation networking technologies such as broadband services, Internet telephony, 3G wireless and web applications and security testing. The Systems group develops power control systems for specialist electrical vehicles in the mobility and industrial markets. Further information about Spirent Communications plc can be found at

Spirent Communications plc Ordinary shares are traded on the London Stock Exchange (ticker: SPT) and on the New York Stock Exchange (ticker: SPM; CUSIP number: 84856M209) in the form of American Depositary Shares ("ADS"), represented by American Depositary Receipts, with one ADS representing four Ordinary shares.

Spirent and the Spirent logo are trademarks or registered trademarks of Spirent Communications plc. All other trademarks or registered trademarks mentioned herein are held by their respective companies. All rights reserved.

This press release may contain forward-looking statements (as that term is defined in the United States Private Securities Litigation Reform Act of 1995) based on current expectations or beliefs, as well as assumptions about future events. You can sometimes, but not always, identify these statements by the use of a date in the future or such words as "will", "anticipate", "estimate", "expect", "project", "intend", "plan", "should", "may", "assume" and other similar words. By their nature, forward-looking statements are inherently predictive and speculative and involve risk and uncertainty because they relate to events and depend on circumstances that will occur in the future. You should not place undue reliance on these forward-looking statements, which are not a guarantee of future performance and are subject to factors that could cause our actual results to differ materially from those expressed or implied by these statements. The Company undertakes no obligation to update any forward-looking statements contained in this press release, whether as a result of new information, future events or otherwise.

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