The decision followed an impassioned debate in the Shadow Cabinet yesterday, which set Michael Howard against David Davis, his Shadow Home Secretay. Mr Davis had argued against supporting the Bill on a series of grounds including cost and civil rights.

Tim Yeo, the Shadow Environment Secretary, was the only senior figure to speak out in support of Mr Davis and against Mr Howard. Mr Yeo was reported as saying that if the Tories were in favour of small government against big government, and of efficient government against bureaucracy, “then ID cards stink”.

Oliver Letwin, the Shadow Chancellor, is also believed to be highly sceptical of the scheme but said little during the discussion.

In order to avoid a backbench revolt on Monday, when the Bill’s second reading will take place, Mr Howard has ordered a two-line whip. That will enable Tory MPs who seriously oppose the Bill to find reasons to stay away without fear of being disciplined. Mr Davis will still have to argue the official opposition line, despite his personal reservations.

As a compromise, which was finally accepted after weeks of agonised discussions, Mr Howard proposed that the Bill be backed as a measure that could help in the fight against terrorism but that the Conservatives should also pledge to attempt to change it as it passes through the Commons. They will also promise to amend the scheme on coming to power if it proves to need changes.

All recent polls have suggested that the public is in favour of ID cards, and a member of the Shadow Cabinet who is doubtful about them said last night that the party could not afford to be positioned on the wrong side in the law-and-order battle.

Tony Blair raised the stakes on the issue by making ID cards the centrepiece of his speech to the Commons opening the new session of Parliament, saying that they were essential to the battle against terrorism, illegal immigration and organised crime.

A statement from the Tory leadership last night said: “The party will give its support in principle at this stage. During the course of the Bill the Conservatives will continue to hold ministers to account over our five tests: the exact purpose of the scheme; whether it will meet those objectives; whether this Home Office is capable of delivering them; the cost-effectiveness of the scheme; and whether proper protection can be provided for privacy.

“But it is important to remember that this Bill will take a decade to come into full effect. It will do nothing to solve the immediate problems of rising crime and uncontrolled immigration.”

The statement said that Conservative priorities were controlled immigration and more police. “In terms of immigration, Parliament will set an annual limit on the number of people settling in the UK. We will reintroduce 24-hour surveillance at Britain’s ports.”

Mr Howard’s move is clearly designed to stop Mr Blair claiming that the Conservatives have blocked the Bill if he calls a general election in May next year.

It is also, however, an attempt to put the Liberal Democrats on the spot. They have said that they will oppose the Bill. Even with Conservative support it will still face strong opposition on civil liberties grounds, particuarly in the House of Lords.

Explore UK News

• Crime News

• Education News

• Health News

• Science News

• Scotland News

Times Recommends

• One case exposes grim reality for thousands
• A glass case: Prince who yearns for action
• Elizabeth Gaskell: I won’t see out the year