Home secretary David Blunkett will today utilise an obscure parliamentary procedure to avoid a full scale debate in the Commons or Lords to push through changes to the US-UK extradition treaty he agreed this year.

The changes remove the right of British citizens facing more than a year in jail to argue that there is no prima facie evidence linking them to the offence.

Charles Kennedy, leader of the Liberal Democrats, said: "The home secretary seems to make a habit of ignoring parliament when it suits him.

"This is a case in point - retrospective legislation should be properly debated in the House [of Commons] - not slipped through in the pre-Christmas rush."