The rise in operating costs throws the success of Gordon Brown’s ambitious Whitehall efficiency drive into doubt.

The jump in the administrative cost of the Government’s bureaucracy — by four times the rate of inflation — was revealed by the Treasury’s own figures.

It was seized on by the Conservatives as the war of words between the parties over tax and spending intensified yesterday.

The Chancellor’s embarrassment was compounded as his own figures showed the running costs of the departments over which he has personal charge rose by 10 per cent.

Doubts about whether Mr Brown is on course to deliver the £21 billion of savings called for in the Gershon efficiency review grew as the Treasury failed to publish its regular annual breakdown of the number of civil servants and other public sector staff.

In a move that will provoke accusations that it is concealing information from voters, the Treasury said that the latest figures would not be released until May 26, three weeks after polling day.

The most recent figures from March showed a rise of 6,000 in Civil Service posts in the first quarter of last year. Mr Brown’s plans call for a cut of 100,000 Whitehall posts, as well as 2.5 per cent cost savings a year. But the Treasury insisted that updated staffing levels would not necessarily be negative.

The Treasury said the administration bill for the Chancellor’s departments was inflated because of costs relating to the merger of the Inland Revenue and Customs and Excise, and the introduction of the child tax credit.

But its figures showed steep rises in running costs in other departments, with increases of more than 30 per cent at the Department for Environment, Food and Rural Affairs, and the Department for Culture, Media and Sport. Costs at the Cabinet Office, which supports the Prime Minister’s work at 10 Downing Street rose 16 per cent.

Oliver Letwin, the Shadow Chancellor, said that Labour was breaking promises to cut bureaucracy. “Here is the starkest possible evidence that Civil Service overhead has been rising rather than falling,” he said.

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