Reform UK is prepared to name an alleged Chinese spy linked to the Duke of York – despite a court order protecting his identity, Nigel Farage has said.

The party is threatening to use parliamentary privilege – which gives MPs certain legal immunities over what they say in the Commons – to reveal who the businessman is in the chamber.

The alleged spy, known only as H6, was described in court as having formed an “unusual degree of trust” with Prince Andrew, and is banned from the UK.

He was first excluded from entering Britain in 2023 by then-home secretary Suella Braverman, with the Home Office saying he was considered to have engaged in “covert and deceptive activity” on behalf of the Chinese Communist Party.

Judges at a specialist tribunal in London on Thursday ruled Ms Braverman had been “entitled to conclude” that he “represented a risk to the national security”.

Prince Andrew needs to be clear and honest. He has made a mistake, he was in a vulnerable period at the time. But now he needs to be properly open about what happened. There needs to be a full, proper investigation by the security services.

Speaking to the Mail on Sunday, Mr Farage said: “The man should be named immediately – otherwise, the whole thing smacks of an establishment cover-up.

“If it’s not resolved in the courts, he should be named in the Commons. It’s clearly in the national interest.”

Labour MP Graham Stringer told the paper it was “ludicrous for this person to remain anonymous in the country he was allegedly spying on”.

Parliamentary privilege protects MPs from legal action and has been used to bring information subject to a court order, like an injunction, into the public domain.

There are limits to the rules – for example, parliamentarians are prevented from discussing active court cases in order to avoid the possibility of influencing a legal outcome.

Former Tory leader Sir Iain Duncan Smith will reportedly seek a Commons debate on Monday over the man’s alleged activities, despite the convention that MPs avoid discussing the affairs of senior members of the royal family.

Sir Iain, a prominent China hawk who has himself been sanctioned by Beijing, said on Saturday: “Prince Andrew needs to be clear and honest. He has made a mistake, he was in a vulnerable period at the time. But now he needs to be properly open about what happened. There needs to be a full, proper investigation by the security services.

“Get ready for project kowtow on steroids. The UK Government crawling on their bellies in obedience. The Government doesn’t want to upset China because they’re ‘so desperate’ over the economy.”

The businessman had brought a case to the Special Immigration Appeals Commission (SIAC) after his initial exclusion in 2023, but his appeal was dismissed on Thursday.

However, the alleged spy has been granted an interim anonymity order which protects his identity.

At a hearing in July, the tribunal was told that an adviser to Andrew had said he could act on the duke’s behalf when dealing with potential investors in China, and that H6 had been invited to the duke’s birthday party in 2020.

A letter referencing the event from the aide, Dominic Hampshire, was discovered on H6’s devices when he was stopped at a port in November 2021.

The letter also said: “I also hope that it is clear to you where you sit with my principal and indeed his family.

“You should never underestimate the strength of that relationship… Outside of his closest internal confidants, you sit at the very top of a tree that many, many people would like to be on.”

On Friday, the duke said he “ceased all contact” with the businessman when concerns were first raised about him.

A statement from his office said: “The Duke of York followed advice from His Majesty’s Government and ceased all contact with the individual after concerns were raised.

“The duke met the individual through official channels with nothing of a sensitive nature ever discussed.

“He is unable to comment further on matters relating to national security.”

The Government has been contacted for comment.