The Norwich and Peterborough operates in East Anglia
The Norwich and Peterborough Building Society has blamed competition from state-aided banks for its decision to close 10 branches.
The mutual, which has 56 branches primarily in East Anglia, also blamed the cost of regulation for adding strain to the sector.
It will close the branches from 5 March next year.
The building society said it wanted to concentrate on its operations in its "heartlands".
The branches that will close are at Kettering, Unthank Road in Norwich, Spilsby, Colchester, Clacton, Chelmsford, Immingham, Halesworth, Ashby and Bedford.
Some 52 members of staff are affected by the closures but there has been no announcement about job losses because the building society said it was hoping to find other roles for some of them.
The announcement came in the same week as the Yorkshire and the Chelsea building societies said they were planning to merge.