MPs last night backed multi-billion pound plans for identity cards despite a revolt by 20 Labour backbenchers in the first test of Tony Blair's shrunken Commons majority.

The Government's majority of 66 was slashed to 31, but the controversial legislation survived to be sent into a standing committee for more detailed scrutiny.

But Labour rebels - including Stockton North's Frank Cook - who joined the Conservatives and Lib-Dems in the No lobby, said they were winning the argument that ID cards were unnecessary, unworkable and too expensive.

One told The Northern Echo: "We are happy to play the long game, because this Bill will implode before it reaches its report stage."

It is possible a special standing committee will take evidence from a wide range of experts before the Identity Cards Bill proceeds, which could provide further ammunition for its critics.

Earlier, Home Secretary Charles Clarke tried to win over backbenchers by pledging the cost of the cards would be capped, possibly at about £100, with discounts for the low-paid.

Mr Clarke said identity cards would reduce the burden of the "Big Brother" society by making it easier for people to open a bank account or board an aircraft.

Only hours before the vote, the Home Office released research suggesting that seven out of ten people would be prepared to pay £100 for a joint passport-ID card.

But Shadow Home Secretary David Davis told the Commons: "It is now clear that ID cards won't fight terrorism, won't tackle crime, won't control immigration and won't stop fraud."

On Monday, a London School of Economics study claimed ID cards could cost up to £19.3bn - way above the Home Office's £5.8bn estimate.

Under the legislation, ID cards would be voluntary until a separate Parliamentary vote around 2010, but ministers have made clear they wish to move to compulsory cards.