Mark Fullbrook, the No 10 chief of staff, accompanied a controversial Libyan politician involved in an attempted military coup to a meeting in the Foreign Office to lobby officials on foreign policy, it has emerged, raising further questions over his influence. Labour has said Fullbrook’s position as Liz Truss’s most senior official is “untenable” after it was revealed that he facilitated unofficial meetings in June with senior cabinet ministers for Fathi Bashagha, a Libyan politician. Bashagha, who is seeking international support as a rival prime minister, has links to the Russian Wagner Group and a military strongman in the east of the country. The Guardian has now established that Fullbrook also accompanied Bashagha on a visit to the UK Foreign Office on the same trip to London, acting as his PR adviser. Truss was foreign secretary at the time. Just one month earlier, Bashagha had unsuccessfully attempted to seize power in Tripoli by force backed by a militia called the eighth brigade, against the UN-backed government. Bashagha and Fullbrook met Stephen Hickey, a director for the Middle East and north Africa, despite it not being a trip officially hosted by the UK government and the UK ambassador to Libya having to clarify that he was not a guest of the UK. During the two-day visit, Fullbrook was helping Bashagha to lobby the government to diverge from the official stance of the UN and back a rival administration in Libya. The Sunday Times revealed at the weekend that Bashagha met Kwasi Kwarteng, then business secretary, and Nadhim Zahawi, then education secretary, at an unofficial appointment in parliament. It also reported that Fullbrook had made efforts to influence Truss, despite No 10 having previously told the Guardian that his company, Fullbrook Strategies, “did not lobby Liz Truss when she was foreign secretary”. Fullbrook worked for Bashagha in the spring and early summer, before joining Truss’s leadership campaign and then entering Downing Street in September. Soon after his visit to London, the foreign affairs select committee held a rare off-evidence session via satellite link with Bashagha. The session was highly unusual, given that the committee was not conducting an inquiry into Libya at the time, it did not seem related to any of its other work, and it largely gave Bashagha a platform to lobby for British support. In his bid for power, Bashagha formed an alliance of convenience with not only the powerful speaker of Libya’s House of Representatives (HoR), but also eastern Libya’s military strongman, Khalifa Haftar, a man accused of war crimes. Haftar’s Libyan Arab Armed Forces (LAAF) laid bloody siege to Tripoli in 2019-20 with the support of thousands of Kremlin-affiliated Wagner Group mercenaries. The brutal and economically hugely damaging siege was only defeated when Turkey intervened to provide military training and equipment to the military forces of the government of national unity. Kwarteng has previously defended Haftar, writing a pamphlet calling for Britain to get behind the strongman. He did so after a visit to Libya during which he met Haftar in conjunction with Leo Docherty, now a Foreign Office minister responsible for Europe. Libya is broadly divided between two sides: one based in Tripoli, dependent on Turkish support and led by Abdul Hamid Dbeibah, and the other based in the east and reliant on the support of Russia and the United Arab Emirates. The UK ambassador in Libya, Caroline Hurndall, has met Bashagha more than once and the UK policy is to focus on the UN-led efforts to get both sides to agree the terms of national elections. Downing Street was contacted for comment on Fullbrook’s role in the meeting. No 10 told the Sunday Times at the weekend that he had recused himself from matters involving Libya. A Fullbrook spokesperson told the newspaper: “These matters relate to Mr Fullbrook’s engagements long before he was involved with any government role. “Mr Fullbrook and Fullbrook Strategies have complied with all legal obligations and have conducted everything in an open and transparent manner. The government was fully aware of all of Fullbrook Strategies’ and Mr Fullbrook’s professional engagements before Mr Fullbrook was appointed as the PM’s chief of staff.” Fullbrook’s position was further destabilised on Sunday when he was forced to recuse himself from discussions about changes to the government’s smoking strategy due to his past as a tobacco industry lobbyist. Fullbrook worked on behalf of British American Tobacco and Philip Morris, the maker of Marlboro cigarettes.