Northern Rock has announced plans to shed 650 jobs by the end of the year.
The Nationalised bank said the move is part of a restructuring plan to align its headcount more closely to a shrunken business.
The lender also said it will try and avoid compulsory redundancies where possible and has entered into a consultation with the Unite union, which claims the total number of jobs losses will exceed 650.
Unite has urged the Government to intervene and has criticised plans to shed more jobs on top of 2,000 already lost since 2008.
Northern Rock, which plans to close its final salary pension scheme, currently employs around 4,500 people.
Although the bank is planning to return to private ownership, it stressed the importance of delivering value for tax payers in the meantime.
The bank - the country's fifth largest mortgage lender at one time - was the UK's first major casualty of the credit crunch when it was taken into public ownership in the Autumn of 2007.
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