Labor has demanded answers about how much Liz Truss knew about her 10th chief of staff, Mark Fullbrook, being questioned as a witness as part of an FBI investigation into alleged bribery.
Deputy Leader Angela Rayner wrote to Cabinet Secretary Simon Case, urging him to clarify when she first learned of the allegations.
He pressed Mr. Case about when the information was shared with Ms. Truss and whether Mr. Fullbrook testified to his involvement in the investigation as a witness when she appointed him as her chief of staff.
The FBI investigation relates to allegations that Conservative Party donor Julio Herrera Velutini promised to help Puerto Rico’s former governor get re-elected if he removed an official investigating a bank he owned there.
Velutini, who has denied the charges, is alleged to have paid the CT Group, a political consulting firm in which Fullbrook was a major figure, around £260,000 for work intended to help the Governor’s re-election campaign which ultimately failed. .
The FBI only treated Fullbrook as a witness, and its spokesman said he “complies with all laws and regulations in any jurisdiction … and is confident that he has done so in this matter.”
Ms Rayner said she was asking Mr Case for answers “in the absence of an independent adviser on ministers’ interests following Lord Geidt’s resignation” in June.
Boris Johnson did not replace him and Mrs Truss indicated she was not interested in appointing an ethics adviser, saying she knew “the difference between right and wrong”.
In her letter, Ms Rayner said the reports about Mr Fullbrook were “incredibly alarming revelations that the public will want clarity on”.
“The allegations about the new prime minister’s senior adviser once again raise questions about this government’s ethics, values and basic standards of decency,” he wrote. “Public trust is already hanging by a thread.”
The Labor MP said: “In the interest of transparency and out of respect for our democratic institutions, I urge you to clarify when you first became aware of these allegations.”
Ms Rayner added: “More importantly, at what stage was this knowledge shared with the Prime Minister? Was there any statement from Mr. Fullbrook about his involvement in this investigation when he took over as chief of staff?
Mrs Truss has given her “full support” to Mr Fullbrook. A Downing Street spokeswoman said the prime minister stands behind him 100 per cent and that he “has his full support”.
Asked if Fullbrook briefed her on the case before she named him chief of staff, Truss told reporters on the plane en route to New York: “All government-appointed personnel go through a proper process.”
A spokesman for Fullbrook said he had “fully, completely and voluntarily engaged with US authorities on this matter.”
The spokesperson added: “The job was hired only by Mr. Herrera and only to conduct opinion research for him and no one else. Fullbrook never did any work for the governor or her campaign, nor did he present any investigative results to her.
“There has been no engagement since then. Mr. Fullbrook understands that there are active legal proceedings against other persons and entities. Therefore, it would be inappropriate to comment further.”