Memos released under the Freedom of Information Act show that aides to Darling asked Treasury officials to cost Conservative policies to help discredit them.
Francis Maude, shadow minister for the Cabinet Office, has written to cabinet secretary Sir Gus O’Donnell asking him to investigate whether Darling’s advisers broke rules designed to stop the politicisation of the civil service.
“It is apparent that Labour has once again compromised the impartiality of the Civil Service and used the taxpayer-funded service for political attacks,” Maude said yesterday.
The documents show that Darling’s aides repeatedly asked for detailed analyses of Tory policies when the country was in the grip of recession.
Many of the costings were later used in a 148-page dossier that Labour published last month in a bid to prove that Tory spending plans were unaffordable.
The dossier – which was dismissed as “dodgy” by the opposition – purportedly showed a £34bn “black hole” in Tory plans.
The memos also show that Darling’s special advisers put pressure on civil servants to produce costings quickly, often asking for information “ASAP” or within 24 hours.
A Treasury spokesman said: “Any costings of opposition policies produced by Treasury officials are produced in line with Cabinet Office guidelines, and are consistent with the practice of successive administrations.”