Atom, which will offer services online and have no branches, is one of a number of new British banks hoping to challenge the dominance of the country's biggest lenders, whose reputations have been hit by a series of scandals.

Chairman and founder Anthony Thomson, who was also a co-founder of Metro Bank, Britain's first new retail bank for over a century, said in June that Atom was planning to raise 75 million pounds before the end of the year.

The bank has opted to initially raise a third of that money and will close that fundraising this week before raising a further 50 million pounds later in the year, the sources said.

The latest fundraising comes on top of 25 million pounds that the bank had already raised from investors including Woodford, venture capitalist Jon Moulton, and the former chairman of Goldman Sachs Asset Management, Jim O'Neill.

It will enable the bank to build its capital ahead of a planned launch of its first product before the end of the year, the sources said.

(Reporting by Matt Scuffham, editing by Sinead Cruise)