Under the terms of the offer, Shawbrook shareholders would receive 330 pence per ordinary share in cash and retain any final dividend for last year, the bank said in a statement.

The shares jumped 18 percent to 316.5 pence on Friday.

The offer is about a 22 percent premium to Thursday's share price.

Britain's so-called 'challenger' banks have been increasingly seen as ripe for takeovers in recent months, bankers who advise on mergers and acquisitions have said, as a prolonged period of low interest rates has squeezed earnings and the pound's fall has made them cheaper for foreign buyers.

Co-Operative Bank, rescued from the brink of collapse by a group of hedge funds in 2013, put itself up for sale last month after struggling to meet regulatory capital requirements.

Pollen Street Capital currently holds 38.9 percent of shares in the British lender, which was founded in 2011 and which was listed in April 2015 at 290 pence a share.

(Reporting By Andrew MacAskill and Lawrence White, editing by Anjuli Davies)