Alistair Darling, UK chancellor, is expected to delay the sale of the healthy parts of Northern Rock until after the general election, it emerged on Tuesday, as the nationalised bank announced half-year losses of almost £725m.

The chancellor said he was in “no hurry” to offload the bank he nationalised in February 2008 but he still believed the rescue operation for the troubled mortgage lender could reap a profit for the taxpayer.