PRIME Minister Tony Blair was battling to win backbench support for identity cards last night amid fresh warnings they will create a "surveillance society" - and cost up to £300 for each card.

At least 21 Labour MPs have signalled they will vote against the plans in a vote tonight, with several more expected to abstain.

The revolt, at a second reading of the Identity Cards Bill, will be the first test of Mr Blair's authority since the Government's majority was reduced to 66.

Yesterday, the plans suffered a double blow when they were criticised in two reports on the grounds of cost, technical feasibility and the safety of confidential information.

An investigation by professors at the London School of Economics (LSE) dismissed Home Office claims that the cards would cost £5.8bn over ten years, or £93 per person. Instead, the study suggested the cost would be at least £10.6bn and could be as high as £19.3bn - or £305 per card - if it ran into technical trouble.

It raised ten concerns, including the need to regularly retest biometrics, non-co-operation from the public, privacy and the security of data.

And it warned the "successful identity theft of a person's biometric data would mean their fingerprints or iris scans are permanently in the hands of criminals, with little hope of revoking them."

In a separate attack, Richard Thomas, the independent information commissioner, condemned the project as "excessive and disproportionate", warning it could create a "surveillance society".

Last night, Stockton North MP Frank Cook said he would either vote against the Government or abstain, having become increasingly concerned about the Bill's implications.

Mr Cook said: "I was pretty firmly in favour of ID cards until a week ago, after all I had one myself as boy during the war. But I'm grievously troubled over what I have heard since then about the abuse of information."

However, Kevan Jones, MP for Durham North said: "ID cards are a sensible measure, given we will have to go over to biometric passports anyway."

Redcar MP Vera Baird said: "The information that will be held is not significantly greater than will be held on driving licences."

At his monthly Press conference, Mr Blair dismissed the LSE's cost estimate as "absurd", but refused to put a cap on the possible cost.

His only concession was to pledge to scrap the legislation if costs did become "unreasonable".

But ministers are today expected to promise cut-price cards for people on low incomes in an attempt to win over wavering Labour MPs.