NORTHERN Rock's nationalisation has added more than £92bn to public debt and breached the Treasury's sustainable investment rule, according to the Office for National Statistics (ONS).

It suggested the move to take the Newcastle- based bank into public ownership helped put the UK's net debt at 43.1 per cent of Gross Domestic Product in March.

That is above the 40 per cent limit dictated by the Treasury rule, although Chancellor Alistair Darling has said any impact on the public finances will be temporary and exceptional''.

The ONS added that it was not possible to give a firm date'' on its final calculations of Northern Rock's impact due to the time taken to gather and check information from the lender. Ron Sandler, the bank's executive chairman, said it could take longer than planned to repay its £24bn debt to the Government if the UK suffers a recession.