Parliament should challenge the government's erosion of civil liberties, former prime minister Sir John Major has said.
Writing in the Times newspaper, Sir John attacks the government's policies on pre-charge detention, identity cards and the 'surveillance society'.
"This is not a United Kingdom that I recognise and parliament should not accept it," he says, criticising the government for failing to justify the proposed increased maximum limit for terror suspects' detention before a charge from 28 to 42 days.
"The government has been saying, in a catchy, misleading piece of spin: 'If you have nothing to hide, you have nothing to fear.' This is a demagogue's trick. We do have something to fear - the total loss of privacy to an intrusive state with authoritarian tendencies."
Sir John has avoided regular comments on the government which succeeded his in 1997 but the controversy over 42 days has seen him add his weight to the debate.
"To appease opposition, the government is cobbling together face-saving compromises. If the measure is passed, it will be a pyrrhic victory that owes more to political survival than principle," he adds.
Sir John criticised plans to introduce ID cards to Britain, saying Britons should fear "the total loss of privacy to an intrusive state with authoritarian tendencies", and said he believes the government's anti-terrorism policies "sometimes come close to scaremongering".
He points out the measures introduced since 1997 have gone beyond those considered by his government, when Britain faced "far more regular - and no less violent - assaults from the IRA".
"No one can rule out the possibility of another atrocity - but a free and open society is worth a certain amount of risk," he concludes.
"A siege society is alien to our core instincts and - once in place - will be difficult to dismantle. It is a road down which we should not go."