The US-UK extradition treaty at the centre of political salvos in Britain was yesterday attacked before the US Senate foreign relations committee by Irish-Americans concerned it would "threaten, intimidate, harass and persecute and terrorise" supporters of the Irish nationalist cause in Northern Ireland.

Tony Blair, British prime minister, has come under intense domestic pressure to secure Senate ratification of the treaty - a necessary step to it taking effect. In 2004, Britain incorporated most of the treaty's new provisions into its own laws, expediting the extradition of British citizens to the US, but did not secure corresponding benefits from Washington.