Sky News has learnt that the company has hired Spencer Stuart, the headhunting firm, to identify a successor to Bridget Rosewell, who has chaired it since 2018.

City sources said the hunt for Ms Rosewell’s replacement formed part of a plan to reshape its board ahead of an initial public offering (IPO).

Mark Mullen, Atom Bank’s chief executive, has spoken for years of a desire to float the company.

A 2024 IPO is now seen as likely.

Atom Bank raised another £30m in equity from leading shareholders including BBVA, the Spanish bank, in November.

It is now understood to be approaching investors about raising at least another £100m in equity, with one insider suggesting it was likely to be closer to £150m.

Mr Mullen said in November that Atom had surpassed £4.5bn in retail deposits “having made waves with the pricing of our fixed and instant savers, opening up a void between banks such as Atom that pay a fair return on savings and those that are simply unresponsive to the market”.

The appointment of a new chair will come soon after Atom also replaced its finance chief, with Andrew Marshall replacing David McCarthy.

Atom has hired bankers to work on its pre-IPO fundraising and subsequent listing.

Last year, talks about a £700m merger involving a vehicle set up by Donald Trump’s former commerce secretary fell apart.

Atom had been in talks with a special purpose acquisition company (SPAC) set up by Wilbur Ross, the billionaire Wall Street financier.

Established in 2014, Atom Bank has raised roughly £500m in equity from investors including BBVA, Toscafund and the now-dissolved Woodford Investment Management.

In 2021, it attracted headlines by becoming one of the first substantial employers to switch to a four-day week.

It said the move, which included a reduction in working hours from 37 to 34 with no impact on salaries, was designed to support employees’ mental and physical wellbeing, as well as to boost productivity.

The Durham-based bank did not respond to a request for comment.