BORIS JOHNSON’S new ministerial ethics adviser made secret trips to the Gulf dictatorship, a Declassified UK investigation revealed today.

Christopher Geidt, former top aide to the Queen, diplomat and army intelligence officer, sat on the Sultan of Oman’s privy council while sitting in the House of Lords — something he never declared to Parliament.

Lord Geidt’s role involved advising Sultan Qaboos on how to run the country’s economy, security and foreign policy, and he made advisory trips to the Gulf state in 2018-2019, Declassified UK found.

The sultan was the Middle East’s longest-serving autocrat: throughout his reign all political parties were banned, independent media was silenced and critics were imprisoned.

Lord Geidt will oversee investigations into whether the Prime Minister and his ministers have been compromised by private interests, including the recent scandal over whence Mr Johnson received £200,000 to redecorate his Downing Street flat.

The Cabinet Office, which appointed Lord Geidt to the new role, said he had done nothing wrong in his dealings with the late dictator, telling Declassified UK: “Lord Geidt has fully complied with his obligations under the code of conduct for members of the House of Lords.”

Lord Geidt’s trips could have cost thousands of pounds by Declassified UK’s calculations, which would breach the code rule requiring lords to register “all relevant interests, in order to make clear what are the interests that might reasonably be thought to influence their parliamentary actions.”

An Omani exile and torture survivor has filed a complaint with the House of Lords standards commissioner to investigate the secret trips.