The government will be accused today by the Liberal Democrats and the Tories of sneaking through retrospective laws that will allow the US to have any British citizen extradited for trial in America without having to prove there is evidence of guilt.

David Blunkett, the home secretary, is using a little known 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 retrospectively 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. Only evidence of identification from US police will be required.

But US citizens accused of murder, rape, robbery and drink-driving offences in the UK will be protected from extradition unless a US judge is convinced there is prima facie evidence against them.

Britain has also agreed that extradited US citizens would not be handed over to the International Criminal Court -- which the US refuses to recognise. David Davis, the shadow home secretary, said: "This seems to be an abuse of democracy. Effectively the government is smuggling a one-sided retrospective change of law through a statutory instrument three days before the Christmas recess."

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."

The change could mean British citizens facing the death penalty for some offences in a number of US states.