Civil servants are being misused by the government in the run-up to the general election, according to the head of the civil service managers’ union.

In a letter to the Times, FDA general secretary Jonathan Baume said Alistair Darling’s use of Treasury costings to attack Conservative spending plans represented misuse of publicly-funded facilities for political purposes.

Baume pointed out that civil servants had been permitted to carry out such work since 1992, but called for an immediate moratorium and a full review of the practice after the general election.

“In the FDA’s views it was misused by the Conservative government in the run-up to the 1997 general election and is being misused now by Labour ministers,” he wrote. “[This was] demonstrated by Alistair Darling’s use of Treasury costings of so-called ‘Conservative promises’, which then formed the basis of Labour Party campaign material.”

He added: “The practice… may just about be defensible during the normal run of parliamentary work. However, we are now in the midst of an election campaign and such exercises are an abuse of civil service resources provided by taxpayers, and threaten to subvert the political impartiality of the service.”

Instead of using official resources, Baume suggests that Labour politicians task an independent body, such as the Institute for Fiscal Studies, with analysing opposition plans.

Speaking this morning, Baume confirmed that he had received no formal complaints from FDA members but said there had been concern over the issue in Whitehall since the autumn.

"There were clear signs of unease during the autumn in the civil service that this kind of approach might be taken by ministers because we have seen it before," he said.