Coventry Building Society has made a non-binding offer for Manchester-based Co-op Bank that values the lender at more than £700 million, according to London media reports.

A deal would result in a merged group with about £90 billion in assets.

Coventry is the UK’s third largest building society by assets. For the year to June 30, 2023, its mortgage balances grew by £800 million to £48.8 billion and its savings balances grew by £3.2 billion to £45.5 billion.

Such a deal that would return the private equity-owned Co-op Bank to mutual ownership.

Coventry, which has about two million members, said: “We remain open to opportunities that may enhance the value and services we offer to our current and future members, but we don’t comment on any public speculation.”

Co-op Bank, which declined to comment, said last month that it was “exploring potential strategic opportunities, the assessment of which is currently at a preliminary stage.”