The government is being too vague about its plans to introduce identity cards, MPs have said.

Chairman of the Commons science and technology committee Phil Willis said the fact that the private sector is speaking openly about its concerns over the programme "should set alarm bells in the Home Office ringing".

The committee's report, published on Friday, said the lack of information released by the government made it "difficult to ascertain the true scope of the scheme and to fully understand how technology will be used within the scheme".

Willis said: "We were encouraged that scientific advice is being sought in a number of areas in the identity cards project but the Home Office needs to make some critical changes.

"There is not the level of confidence in this scheme that could be expected at this stage.

"Despite their vested interests in the scheme, industrial representatives are speaking openly about their concerns regarding the identity cards programme - this should set alarm bells in the Home Office ringing.

"Too many aspects of the identity cards programme are unclear: costs, acceptable technology performance levels, plans for the ICT system and the scope of the scheme.

"As a matter of urgency and to increase public confidence, the Home Office must give a clearer idea of what identity cards will be used for if the right technology is to be put in place."

The committee said it was not clear how the cards would be used, what personal data will be revealed in different situations and how the procurement process for the project will work.

The report also said the technical success of the scheme could be jeopardised by 'function creep', as more Whitehall departments decided they wanted to be able to use the cards.

It said the Home Office was following 'best practice' in treating scientific advice and evidence in some areas, but in others - notably biometrics - it was inconsistent.

And it also questioned the Home Office's estimate that annual running costs would be £584m.

That figure has been disputed by research from the London School of Economics, which suggested implementation and running costs would total £10.6bn to £19.2bn over the first 10 years.

The report said: "Given that extensive trialling is still to take place, we are sceptical about the validity of costs produced at this stage.

"We acknowledge that the release of firm overall costing has been driven by political imperatives, but the Home Office could have credibly given a broad range instead of precise figures."

On Thursday prime minister Tony Blair insisted ID cards would form a "major" plank of Labour's next general election manifesto, insisting they were the only way to tackle illegal immigration and crime.

Opposition parties have come out against the plan, as have civil liberties groups.

Shadow home secretary David Davis said the report was "a shocking indictment of the shambles that is the government's proposed ID card system".

"It shows a reckless lack of focus and attention to detail by the Home Office," he added.

"It beggars belief that the government is prepared to waste £19bn of taxpayers' money on this plastic poll tax when the project is already in such dire straits."