Jeffrey Epstein described Peter Mandelson as “devious” after lobbying a bank to underwrite a mining project launched by their mutual friend Nat Rothschild, emails included in the latest tranche of Epstein files suggest.

In April 2010, the then business secretary appears to have contacted banker Jes Staley, then at JP Morgan, from his personal email account in what appears to be an attempt to secure funding for Rothschild, Mandelson’s longtime friend.

Mandelson wrote to say that he was pleased to hear that JP Morgan was “planning” to underwrite a £700m investment vehicle being launched by Rothschild, a scion of the banking dynasty.

“I’ve been following my friend Nat Rothschild’s plans to list a vehicle on the [London Stock Exchange] and I’m very happy that JPM are now planning to get involved as book runners alongside [Credit Suisse],” Mandelson wrote to Staley. “I think it’s a great idea from what I see of the global mining business (and their prices). I hope it all goes well. Best Easter greetings to you and your family.”

Mandelson appears to have shared the communication with Epstein, who was a close friend of Staley’s, adding that he hoped “Jes can send warm response to this informal email”. Epstein responded: “You are sooooooooooooooo devious”.

The emails appear to suggest that Mandelson was using his influence as business secretary to encourage Staley to go ahead and back Rothschild’s venture.

The Labour cabinet minister had seemingly lobbied the US government on behalf of Epstein and Staley a month earlier.

According to emails released by the US Department of Justice in recent days, Mandelson used the two men’s proposed talking points in discussions with Larry Summers, then director of Barack Obama’s National Economic Council about financial-crisis reforms.

He then appears to have leaked private government memos about his meeting with Summers to Epstein, according to the documents.

“I would like you to ask Larry Summers if he would meet directly with Jes, and another jpm person, re the proposed volcker rule. I can’t do it directly,” Epstein wrote to Mandelson, who was both the UK’s business secretary and de facto deputy prime minister. “Larry is getting info third and fourth hand from senators who are getting it from lobbyists.”

Mandelson replied: “I can say this to him.”

The following day, Mandelson asked Epstein whether Staley could “send me email on issues re Dodds/Volcker”.

A subsequent memo apparently from a meeting between Mandelson and Summers suggested that Mandelson had brought up a talking point suggested by Epstein during the meeting.

The document said the chancellor, Alistair Darling, had been “grateful for your [Mandelson’s] intelligence”.

The Volcker rule was introduced in response to the 2008 financial crisis with the intention of preventing major banks from using their own money for riskier trading activities.

The emails suggest that Mandelson was acting on behalf of his friends and associates while in one of the most senior positions in government.

This week Mandelson, who is facing a police investigation after a referral by the Cabinet Office over claims that he had leaked sensitive government documents to Epstein, had said he had always acted in the interests of industry rather than individuals.

He said: “My conversations in government at the time reflected the views of the sector as a whole not a single individual.”

According to emails published by the DoJ, Mandelson was given $75,000 in 2003 and 2004 by Epstein, who he described in separate communications as his “chief life adviser”. He has said he has no record or recollection of these payments.

Mandelson has confirmed that his partner at the time, who is now his husband, Reinaldo da Silva, received thousands of pounds from Epstein in 2009 and 2010.

On Tuesday, Downing Street said the Cabinet Office had referred Mandelson to the police and that officials had handed over an assessment of some of emails found in the Epstein files.

Mandelson said he had been acting in line with the British government’s position on the Volcker rule.

“UK government policy, while recognising the need for regulation, was opposed to the Volcker rule, that it went too far and was too restrictive,” he said. “So we agreed with JPM and other US banks and were happy to lobby against it.”

Mandelson said he had “no recollection” of sending the email to Staley in relation to Rothschild’s investment vehicle.