The Government was accused of using Tony Blair's resignation announcement to bury bad news today, as it disclosed a £400 million increase in the cost of the ID card scheme and cut nearly 400 jobs from the Department of Work and Pensions.

The Conservatives said it was no coincidence that the Home Office chose today to publish the latest increase in the cost of ID cards, more than a month after the information was supposed to be placed before parliament.

The Home Office admitted today that scheme would cost £5.31 billion from 2006 to 2016, an increase of £400 million in just six months since the last estimate was published. The Tories and the Liberal Democrats said the actual increase would be closer to £600 million and called on Gordon Brown to dump the project when he is expected to take over as Prime Minister next month.

“The public will see through this transparent and pathetic attempt to bury bad news," said David Davis, the Shadow Home Secretary. “It is also no surprise the Government has had to revise their cost estimate up by so much."

"The public should brace themselves for more increases every time this estimate is updated."

The Conservatives have angered the IT industry in recent months by repeating their promise to abandon compulsory ID cards should they win the next election. The Liberal Democrats today accused the Government of breaking the law in being more than a month late delivering its latest obligatory update on the scheme's cost.

“That shows the depths of cynicism and media manipulation to which ministers are now resorting to ram this increasingly unpopular scheme through," said Nick Clegg, the party's home affairs spokesman. “To add insult to injury, the statement itself is a laughable cocktail of statistical sophistry and contradictory claims."

The Home Office defended the cost estimate published today, saying the increase of £40 million a year had been caused by "extra staff carrying out vetting, as well as extra anti-fraud measures". The delay was blamed on rules that forbid the publication of politically contentious statistics during the recent local government election campaign.

The Prime Minister's much-publicised decision to step down on June 27 was also described as a handy cover for the news that the Department of Work and Pensions, the largest Government department, is to close three offices today, with the loss of 380 jobs.

The Public and Commercial Services union said that the Government's targets for recovering overpaid benefits would be significantly undermined by the closures. “It is scandalous that this announcement has been slipped out when all eyes are on the departure of Tony Blair," said Mark Serwotka, the union's general secretary.

"Staff are already struggling to hit targets in overpayments due to a lack of resources and unstable IT systems. Cutting staff and closing offices at the same time as increasing the amount to be clawed back in the name of efficiency are the economics of the madhouse."

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