LIZ TRUSS'S most senior adviser has been interviewed by the FBI as a witness in relation to an alleged plot to bribe an American official and influence a US election, it emerged yesterday.

Mark Fullbrook, 60, who ran the Prime Minister's leadership campaign and is now chief of staff at No 10, was questioned about work he did for the banker accused of the crime.

Mr Fullbrook provided research in 2020 for Julio Herrera Velutini, a Venezuelan-Italian banker now accused of bribing the governor of Puerto Rico around the same time.

Mr Fullbrook has said he did not break the law and was not aware his then client may have had corrupt motives for hiring him as a political consultant.

According to a US indictment, Mr Herrera Velutini, a Mayfair-based Tory party donor, allegedly promised Puerto Rico's governor, Wanda Vázquez Garced, $300,000 for her re-election campaign in 2020 provided she sacked the head of the island's financial regulator.

The watchdog was probing Bancredito, the bank Mr Herrera Velutini owns, and according to the indictment, the Governor agreed.

Mr Herrera Velutini denies wrongdoing and is contesting the charges against him, which carry a total maximum penalty of 20 years in jail.

He was paying CT, a consultancy founded by Sir Lynton Crosby, who has helped run several Conservative campaigns in the UK, for services that may have helped the Governor with her re-election bid.

The Sunday Times reported Mr Fullbrook was the lead consultant on the project and flew to Puerto Rico in February 2020, before the election.

Vazquez Garced sacked the financial regulator in February 2020, but lost her re-election campaign in August that year.

According to the US Department of Justice's indictment, Mr Herrera Velutini then tried to bribe her successor, by offering funding in return for a favourable audit of his bank.