British Prime Minister Theresa May on Friday promoted a largely unknown junior health minister, eurosceptic Stephen Barclay, to be her new Brexit Secretary.

He becomes the third person to hold the job overseeing Britain's withdrawal from the European Union, after his two predecessors, Dominic Raab and David Davis, both quit in protest at May's approach.

A trained lawyer, Barclay has been an MP since 2010 and his previous job covered issues of health procurement, workforce pay, and contracts.

Previously, he held a key role in the Treasury, responsible for financial services.

Before becoming a politician, he worked as an insurance company lawyer for Axa Insurance and as a regulator for Britain's Financial Services Authority.

He also worked at Barclays Bank as director of regulatory affairs and head of anti-money laundering.

Married, with two children, he represents the eastern English constituency of north-east Cambridgeshire.

His appointment follows Raab's resignation on Thursday over the Brexit deal struck with the EU.

Raab himself was only appointed in July after Davis quit, also complaining about May's strategy.

Barclay now has the task of steering legislation implementing the Brexit through a hostile parliament.

His department also leads planning for the risk that the process collapses and Britain leaves the EU on March 29, 2019 without any deal in place.