The Financial Conduct Authority (FCA) said it related to figures published by the bank in October 2018 that it "was aware at the time" were wrong.

The challenger bank later said in January 2019 it had corrected risk weightings of some of its commercial loan portfolios.

The announcement wiped hundreds of millions of pounds off its share value and led top bosses to quit.

The FCA said on Monday it had also decided to fine Metro former chief executive Craig Donaldson and former chief financial officer David Arden £223,100 and £134,600 respectively for being "knowingly concerned" in the bank's rule breach.

The pair have referred their cases to the upper tribunal for consideration, meaning the financial penalties against them are provisional, pending a formal hearing.

Metro Bank, which focuses on seven-day per week branch services at a time when its biggest rivals are shrinking high street services, did not refer its own case for further consideration.

It informed investors last week it had increased its provision for an FCA fine to £10m from £5.3m.

The penalty is not the first it has received for the episode.

It was fined £5.4m by the Bank of England's Prudential Regulation Authority last year for failings in its regulatory reporting at the time.

Mark Steward, the FCA's executive director of enforcement and market oversight, said: "Listed firms must ensure that the information they are disclosing to the market is right.

"This is what investors are entitled to receive."