Metro Bank has received a takeover approach from US private equity firm Carlyle.
The move comes after the Co-operative Bank, owned by a group of hedge funds, made an approach for TSB.
Metro, which made a £110m loss in the first half of the year, has 2.4m customers and £16.4bn in deposits. It was created in 2010 by Vernon Hill in the aftermath of the financial crisis, becoming the first new bank in Britain in 100 years.