A former head of the British army has joined a lobbying firm run by the veteran Conservative party strategist Sir Lynton Crosby as it seeks to capitalise on business deals in the defence industry. Gen Sir Mark Carleton-Smith, who until last year was one of the UK’s most senior military officers, will work as an adviser at Crosby’s influential Anglo-Australian consultancy, CT Group. The company announced this week that Carleton-Smith would support its work helping clients take advantage of “commercial opportunities” arising from the Aukus defence pact between Australia, the UK and the US. Under the trilateral agreement, Australia will buy a fleet of nuclear-powered submarines from the US and work with its American and British allies on developing a new class of submarine. The complex multi-decade deal, which has been described as a “bonanza” for defence contractors, is expected to generate tens of billions of dollars of spending by the allies on technology, weapons and shipbuilding. On Monday, Carleton-Smith heralded CT Group’s premium “Aukus Advantage” service, which the company said would help “position clients to gain long-term business advantages from the Aukus framework”. In a promotional video, Carleton-Smith said the company could help clients to identify opportunities with the support of CT Group’s “peerless political, business, defence and intelligence networks”. Carleton-Smith is the latest retired general to move into business after leaving the military. Campaigners on transparency and the arms industry have previously raised concerns about the “revolving door” between the armed forces and the defence industry. CT Group was co-founded by Crosby, the Australian strategist credited as the mastermind behind a series of Conservative election campaigns. Multiple former employees have subsequently moved into senior roles in the Tory party and the UK government. The company helps political clients around the world fight election campaigns and advises corporate clients on lobbying governments. In recent years it has expanded into the defence and security sector, establishing a private intelligence business. Carleton-Smith served until June 2022 as chief of the general staff, a position that placed him at the highest levels of military decision-making and gave him direct accesses to the defence secretary and the prime minister. The former army chief, an Old Etonian who has occasionally played cricket with Boris Johnson, was previously the director of the UK’s special forces and has held senior posts at the Ministry of Defence. On Tuesday, the Advisory Committee on Business Appointments (Acoba) gave a green light to the appointment but said that for two years from his last day in public office Carleton-Smith’s role “should be limited to CT Group’s work outside the UK and he must not advise on the UK defence sector”. A spokesperson for CT Group said that since his departure from crown service over 12 months ago, Carleton-Smith had “engaged extensively” with Acoba, which was “fully satisfied with the appointment and the role”. They said Carleton-Smith was “a distinguished individual who has served the United Kingdom in the highest positions, to the highest of professional standards. His integrity is beyond reproach.”