Sir Keir Starmer will be “completely exonerated” over the scandal around Peter Mandelson’s relationship with disgraced financier Jeffrey Epstein, Gordon Brown has told Sky News.

The prime minister was forced to sack Lord Mandelson as the UK’s ambassador to the US last Thursday after details of the peer’s relationship with Epstein emerged in the media.

Emails between Lord Mandelson, a minister under Tony Blair and Mr Brown, and the convicted sex offender revealed that the ex-minister sent messages of support to Epstein even as the US financier faced jail for soliciting prostitution from a minor in 2008.

Politics latest: PM speaks for first time since Mandelson sacking

Sir Keir said on Monday that he would have “never appointed” Lord Mandelson as US ambassador if he knew then what he knows now.

But Mr Brown told Sky News’ Darren McCaffrey that he believes the prime minister will be “completely exonerated” once “the record is out” on the matter.

The former prime minister said: “I don’t want to criticise Sir Keir Starmer’s judgement, because he faces very difficult decisions and we’re talking about a very narrow area for timing between a Tuesday and Thursday.

“I think once the record is out, Sir Keir Starmer will be completely exonerated.”

However, Mr Brown did admit that the situation “calls somewhat into his judgement”.

He said: “I think every government goes through difficulties. Probably 15 years ago, when I was in government, you’d be asking me questions about what had happened on a particular day.

“But this is not really in the end about personalities. In the end, it’s about the policies.

“If you ask people in the street, they might say, well, interesting story, terrible thing that happened to these girls, but also they will say, look what’s happening to my life at the moment, what’s happening to my community, what’s happening to my industry, what’s happening to the whole region.

“I think we’ve got to think that politics is about changing people’s lives and making a difference in those areas where they want to do things.”

Sir Keir has insisted that Lord Mandelson went through a proper due diligence process before his appointment.

However, speaking publicly for the first time since he sacked Lord Mandelson on Thursday night, he said: “Had I known then what I know now, I’d have never appointed him.”

Sir Keir said he knew before Prime Minister’s Questions on Wednesday afternoon that Lord Mandelson had not yet answered questions from government officials, but was unaware of the contents of the messages that led to his sacking.

He said Lord Mandelson did not provide answers until “very late” on Wednesday, which was when he decided he had to be “removed”.