A verdict on whether plans for a new investment vehicle for Northern Rock’s assets will mean the bank goes on to the government’s balance sheet is expected from the Office of National Statistics.

Chancellor Alistair Darling unveiled a plan to securitise part of the bank’s loan book this week, by selling chunks of the bank’s assets while retaining much of the risk.

Darling told the Commons: ‘It is for the independent Office of National Statistics to determine whether Northern Rock is classified to the public sector in the national accounts.

‘Any liabilities classified to the public sector would be temporary and backed by significant assets and do not represent any meaningful measure of fiscal sustainability.

‘The Code of Fiscal Sustainability ­ underpinned by legislation passed by this House of Commons ­ provides for such situations.’

Opposition politicians have maintained the move was an ‘accountancy trick’ designed to help the government avoid the embarrassment of ‘nationalising’ the bank.

Liberal Democrat Treasury spokesman Vincent Cable said: ‘This is an accountancy trick. The government is determined to present this as not nationalisation ­ the dreaded N-word ­ but this is what it in effect amounts to.’