LIZ Truss’s chief of staff his being paid through his lobbying company which could reportedly allow him to pay less tax.

The alelgations come afer it was revealed Mr Fullbrook was interviewed by the FBI in conenction with an alleged political consipracy in the United States.

According to the Sunday Times, Mr Fullbrook has stressed he is not being paid through his company for tax reasons and has insisted that he has obtained no tax benefit from the arrangement.

The newspaper reports that Mr Fullbrook is refusing to explain the agreement that lets him direct government strategy without being directly employed by the UK Government

Instead of the previous role-holders and other special advisers, who are on temporary civil service contracts with a public salary, Mr Fullbrook has been hired as a contractor.

The equivalent post under Boris Johnson carried a salary of £140,000.

He will instead be paid through his private lobbying company, Fullbrook Strategies, which Mr Fullbrook reportedly has suspended commercial activities.

Between April and June, according to the Office of the Registrar of Consultant Lobbyists, Mr Fullbrook’s company contacted the UK Government on behalf of clients such as the Libyan House of Representatives, which is opposed by the West and the UN, an energy provider and a PPE firm linked to a fundamentalist Christian sect, according to the Sunday Times.

The news emerged just two days after Chancellor Kwasi Kwarteng scrapped the IR35 reforms set up to stop people paying themselves via a company to avoid paying tax.

Dan Neidle, a tax expert and the founder of Tax Policy Associates, said: “I don’t understand why someone would do it.

“Before yesterday, responsibility for applying IR35 [rules] — and liability for getting it wrong — would have fallen on the civil service. I’d expect them to take a very conservative view.

“The effect of the budget change is that Mr Fullbrook gets to decide himself. Of course [it is] subject to later HMRC challenge, but it still gives him an ability to take a more aggressive view than the civil service would have permitted.”

Mr Fullbrook has also been interviewed by FBI agents in connection with an alleged conspiracy to bribe a US politician and influence the outcome of an election in Puerto Rico.

He has since signed an agreement with US law enforcement and is co-operating as a witness. It is understood that he is not under investigation. He denies any knowledge of the bribe and in a statement says he is “confident” he behaved within the law at all times.

Mr Kwarteng was asked by the BBC about the lobbying allegations against Mr Fullbrook.

He said: “I don’t know anything about Mark’s arrangements.

“I think he’s a great professional, I think he’s someone who has enhanced our government, he’s a great person to work with.

“But I don’t know anything about his renumeration and how that’s organised.”