The small US lender has lost in excess of Â£20 million in its initial 16 months of existence on British shores, the Daily Telegraph reports.
Accounts filed with Companies House showed that the group's pre-tax losses stood at Â£23.4 million ($32.1 million) for the 16 months to December 31st 2010.
The bank - whose branches differ from most institutions by opening on Sundays - has four outlets in London and harbours plans to increase this number.
It stated the performance was "a direct result of significant investment across the business in building infrastructure and systems to enable future growth and scale to be achieved".
Further expansion by the bank this year is expected to cost in the region of Â£13 million, which is being financed by numerous private share placements.
Metro Bank was the first new High Street bank in Britain for more than 100 years and aims to be open early until late every day of the week.
By Claire Archer