Tony Blair has praised the appointment of George Osborne as Editor of the London Evening Standard as he said it would make politics "more interesting."
The former Labour prime minister, who has taken up a number of jobs since leaving Parliament, said the former Tory Chancellor was a "highly capable guy."
His comments will increase concerns in Downing Street that Mr Osborne is plotting to use his new role to undermine Theresa May's plans for a clean Brexit by establishing a "new power base" at the newspaper.
Leading figures from the Remain campaign have been accused of seeking to establish a new platform to campaign against Mrs May's plans to leave the Single Market.
Mr Blair, the former Labour Prime Minister, vowed to fight "frightening authoritarian populism" last week as he launched a new think tank which aims to frustrate Mrs May's plans for Brexit.
Asked about Mr Osborne's new editorship, Mr Blair told the BBC's Andrew Marr Show: "I think its a great thing for the Evening Standard. Why not?
"He's a highly capable guy and it should make politics more interesting."
In a direct warning to Mrs May, Mr Osborne said that the newspaper would be "fearless" confronting the Government if it fails to represent the interests of Londoners."If it isn't, we'll be quick to say so," he said.
A senior Government source told The Daily Telegraph: "It's all about establishing a power base. He lost the argument last year in the referendum, he lost influence in Parliament.
The Sunday Telegraph revealed today that Parliament’s sleaze watchdog will consider banning MPs taking second jobs next month.
MPs on the parliamentary Committee on Standards will demand the rules are tightened after a backlash over Mr Osborne’s new role.
Mr Osborne now has six jobs - editing the Evening Standard, advising the financial giant BlackRock, doing after dinner speeches, completing a fellowship in America, chairing the Northern Powerhouse Partnership and being MP for Tatton.