A former aide to Nigel Farage faces up to 20 years in jail in the US after admitting attempting to defraud criminals on the "dark web" by masquerading as a money launderer.
George Cottrell posed as a "financier" on a black market network where he offered to help transfer the ill-gotten gains of drug traffickers, according to court documents.
However his prospective clients were in fact undercover agents, and Cottrell was arrested as he and the former Ukip leader travelled back to Britain following a trip to the US.
The former aide, who is in his 20s, was charged with a string of offences including blackmail, extortion, money laundering.
He now faces up to two decades in jail and a fine of up to 250,000 dollars (£203,000) after reaching a deal with prosecutors.
At the time of his arrest at Chicago's O'Hare airport Ukip described Cottrell as "an unpaid and enthusiastic volunteer for the party over the period of the referendum".
The party has declined to comment on his confession.
A plea agreement filed by prosecutors in Phoenix, Arizona, in December, states that Cottrell admitted to communicating with the "traffickers" on March 27 2014.
He said he had contacted individuals in Phoenix from London and worked with an associate called "Banker".
Cottrell said: "I explained various ways criminal proceeds could be laundered – for example, methods to transfer large amounts of cash out of the United States without triggering reporting requirements and ways to disguise the proceeds as legitimate business income for tax purposes.
"I falsely claimed that I would launder the criminal proceeds through my bank accounts for a fee. Rather than launder any of the money, though, Banker and I intended to retain the money."
Cottrell had faced 21 charges but these were reduced to one count of wire fraud as part of the plea bargain.
In court documents prosecutors said that around March 2014 Banker had advertised "money laundering consultation services" on an clandestine network using software called TOR (The Onion Router).
"Undercover law enforcement agents contacted Banker, posing as drug traffickers seeking money laundering services for approximately 50,000 to 150,000 (£120,000) dollars per month in drug trafficking proceeds," prosecutors said.
"Banker agreed to help the undercover agents launder their money for a fee, and then proposed that the undercover agents speak with his associate, 'Bill'.
"The undercover agents talked with Banker and Bill on March 27 2014, via an encrypted group messaging platform online. Bill agreed to launder the undercover agents' purported drug proceeds by transferring the property to offshore accounts 'with complete anonymity and security'.
"The undercover agents then met with Bill – later identified as George Swinfen Cottrell – in person in Las Vegas, Nevada."
Cottrell, who comes from a wealthy, aristocratic family, was arrested as he returned from the Republican Party convention with Mr Farage on July 22.
After his success in the EU referendum, the former Ukip leader spoke at a fringe event at the convention that later saw Donald Trump nominated as the Republican candidate for the White House.
Cottrell's uncle Lord Hesketh, a former hereditary peer, worked for former prime minister Margaret Thatcher before losing his seat in the Lords in 1999 as a result of the House of Lords Act. He later defected to Ukip.
Cottrell's mother, Fiona Cottrell, is the daughter of another peer.
A Ukip spokesman said at the time of his arrest: "George was an unpaid and enthusiastic volunteer for the party over the period of the referendum.
"We are unaware of the details of the allegations excepting that they date from a time before he was directly involved in the party."
On Monday a Ukip spokesman said: "We are not commenting on the matter."
The spokesman was unable to confirm whether or not Cottrell was a member of the party. He will reportedly be sentenced in March.