Image copyright Getty Images Image caption Nigel Farage addressed this year's Republican convention

An aide to former UKIP leader Nigel Farage is facing blackmail and money laundering charges in the US.

George Cottrell was arrested at the airport, as he was attempting to travel back to the UK with Mr Farage.

He was allegedly caught in an FBI sting operation agreeing to launder money for undercover agents posing as drug traffickers.

A UKIP spokesman said the alleged offences date from before Mr Cottrell was directly involved in the party.

According to the Associated Press news agency, Mr Cottrell is facing 21 counts relating to money laundering, fraud, blackmail and extortion.

An Arizona federal indictment said that in 2014 he agreed to launder the purported drug proceeds of undercover FBI agents by transferring them to offshore accounts.

He later met the undercover agents in Las Vegas, arranging for them to transfer 20,000 US dollars (£15,500) to an associate, the indictment says.

He was arrested on 22 July at Chicago's O'Hare airport as he attempted to return to the UK with Mr Farage after they had visited the Republican Party convention in Cleveland.

Mr Cottrell, who is in his 20s, is also alleged to have tried to blackmail the fake drug traffickers by threatening to report them to the police unless they paid him 130 Bitcoin, then worth around 80,000 dollars (£62,000), according to the indictment.

A UKIP spokesman said: "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."

Mr Cottrell has been denied bail by a judge who said he "poses a serious risk of flight".

His uncle, Lord Hesketh, is a former hereditary peer, who 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. The peer later defected to UKIP.