Members of the Britannia Building Society have backed moves to merge the business with the financial services arm of the Co-operative.

More than 450,000 Britannia members voted at the society’s annual meeting in Birmingham yesterday, with 88.6 per cent of savings members and 86.2 per cent of borrowers in favour.

The vote required the support of more than 75 per cent of savers and 50 per cent of borrowers.

The merger, which has already been approved by the Co-operative Group, was first announced last October. It is expected to become effective on August 1 subject to confirmation by the Financial Services Authority.

In the first-ever merger between different types of member-owned businesses, the “super-mutual” will have £70 billion of assets, nine million customers, 12,000 employees, more than 300 branches and 20 corporate banking centres.

It will be led by Britannia group chief executive Neville Richardson. Bob Burlton, the Co-op Financial Services chairman, will chair the new board.