Gordon Brown has raided the health, education and transport budgets to fund 30,000 extra “social” homes in a hastily assembled relaunch heavily influenced by Lord Mandelson.

There was immediate confusion in Whitehall last night as departments appeared not to be aware that they were supposed to be funding the £1.5 billion centrepiece of the Government’s pre-election fightback.

The plan to increase to 110,000 the number of social homes built over the next two years was the only significant expenditure outlined by Mr Brown yesterday as he fought to regain the initiative with a draft programme of 11 Bills for the last session of Parliament before polling day.

Downing Street signalled that half the cost would come from the Department for Communities and the rest from “underspends” elsewhere.

Within hours the sums were being challenged. The Department for Communities refused to accept that it would foot half the bill and seemed to be fighting a proposal to plunder its Decent Homes refurbishment programme. Whitehall sources repeatedly told The Times that no agreement had been reached, amid warnings that the move would leave at least 200,000 council homes in disrepair.

Officials at the Schools Department were also taken by surprise. The Department of Health implied that the money could come from a £350 million underspend in capital projects this year, but had no details. The Home Office is providing nearly £50 million. The Department for Transport said that money would be raised from underspending on the widening of the M25 — a project that has been in dire financial difficulties.

Tony Travers, a local government expert at the London School of Economics, said: “It would be a tragedy if the money were taken from the noble endeavour of tackling a legacy of very poor housing stock to create the appearance of a spending boost.”

David Cameron said that Mr Brown was living in a dream world. David Gauke, the Shadow Treasury Minister, said: “This relaunch has been exposed as being more about propping up Gordon Brown’s future than about the future of Britain.”

The only other fresh spending announced yesterday was £150 million to boost investment in biotechnology and low-carbon research.

Times Recommends

• Postmen: We bind the nation together
• Tewkesbury: when the memories flood back
• Cast Offs actress: I’m happy that my face fits