Mandelson still faces the possibility of a Metropolitan Police investigation into misconduct in public office.
The peer, who was serving as Business Secretary in Gordon Brown’s Cabinet, shared market-sensitive information with Epstein that the paedophile could have used to make money.
The disclosures included plans for a multibillion-pound EU bailout, Brown’s resignation and the potential sale of government land and property.
In one email sent by Mandelson to Epstein in 2009, the then Business Secretary forwarded an economic briefing for Brown with the caption: “Interesting note that’s gone to the PM.”
The memo, which was written by Nick Butler, a special adviser, and began “Dear Gordon”, contained an assessment of the state of the economy after the financial crisis.
It contained a reference to the Government having “saleable assets in hand”, and Epstein asked Mandelson: “What saleable assets?” He replied: “Land, property I guess.”
Another email chain, sent by Jeremy Heywood, the No 10 chief of staff at the time, to Baroness Vadera, then Business Secretary, and copied to Mandelson, was also leaked to Epstein. However, the name of the leaker was redacted in files released by the US Department of Justice.
Further emails from 2010 showed Lord Mandelson appearing to confirm to the financier, who died by suicide in 2019, details of the EU’s €500 billion ($973b) bailout deal on May 9, several hours before it was publicly announced.
He also appeared to forward to Epstein an economic briefing note that had been sent to Brown earlier that year. While the note was unclassified, it related to Mandelson’s role as business and trade secretary.
A Downing Street spokesman said on Tuesday afternoon that it was “right” for Mandelson to step down from the House of Lords.
He added: “As the Prime Minister said ... Peter Mandelson let his country down.”
Earlier on Tuesday, the Cabinet Office confirmed it had sent the Met Police an assessment of how the emails were supposed to be kept confidential.
Mandelson has resigned under the House of Lords Reform Act 2014, relinquishing his peerage. However, this will not strip him of his title, and an act of Parliament must be passed to do so.
The Titles Deprivation Act 1917, which would remove Mandelson’s title, was last used in 1917 against a group of peers who had aided enemies of Britain during the war.
On Tuesday, No 10 opened the door to wide-reaching Lords reform that would make it easier for peers to be stripped of their titles. A spokesman for Starmer said there was no other walk of life in which employees could be similarly “unsackable”.
Mandelson resigned from the Labour Party on Sunday night, claiming that this was to avoid “further embarrassment” to Starmer and his colleagues.
Images of the peer in his underwear were released as part of the latest tranche of the Epstein files last week.
He is seen wearing what appears to be a pair of white Y-fronts and a T-shirt in 11 images. He is pictured next to a woman in some of the images whose face was redacted.
Shortly after Mandelson resigned, a Labour spokesman claimed that internal disciplinary proceedings had been launched, although he declined to say when they would take place.
Last month, the peer refused to apologise to Epstein’s victims for maintaining his friendship after he was convicted of sex offences.
He argued that he was not culpable for any of Epstein’s criminal activity, and claimed that being gay meant he was kept in the dark about the full horror of his crimes.
However, this position lasted less than 48 hours until he issued a statement saying he was “truly sorry” that he had believed his friend over his victims.
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