The Conservative peer Greg Barker has resigned as chairman of EN+, the mining company part-owned by the sanctioned Russian oligarch Oleg Deripaska. Lord Barker, an energy minister in David Cameron’s government, oversaw a plan to help the firm respond to US government sanctions levelled against the company and Deripaska in 2018, when it sanctioned the oligarch over his alleged links to the Russian government. Deripaska has previously said the US allegations were based on “false rumour and innuendo”. Barker’s resignation comes amid intense scrutiny of companies linked to sanctioned Russian oligarchs, alleged by authorities in the US, EU and UK to be part of the system through which Vladimir Putin controls the Russian economy. After Russia’s invasion of Ukraine, the London Stock Exchange last week suspended trading in EN+ along with more than 30 other Russian-linked firms, “in light of market conditions, and in order to maintain orderly markets”. While Barker will step down as chairman of the listed company, EN+ confirmed on Monday reports that it was considering carving out a large part of the aluminium business, which included the part-owned subsidiary Rusal. The new company would be owned by management and non-Russian investors, and potentially led by Barker, according to a report by Bloomberg News that was referenced by EN+. It would take on Rusal’s alumina, bauxite and aluminium assets across the world, including in Africa, Australia and Europe. Barker’s role with the company has always been controversial but pressure has increased in recent days amid strong criticism from Conservative party colleagues and scrutiny on directorships in companies linked to Russian oligarchs. The UK defence secretary, Ben Wallace, said last month Barker should quit all Russia-related roles. “I think Lord Barker should explain why he works with people like Deripaska,” he said. Barker had served as a minister for energy and climate change in Cameron’s government but he has since earned millions of pounds for chairing EN+, including $7.8m in salary and bonuses in 2019 after he conceived the “Barker plan” to avoid US sanctions directly on the company. EN+ is still thought to make monthly reports to US authorities to ensure it is not breaching the terms of the agreement. In a statement to the stock market, EN+ said: “The group confirms that it is currently reviewing its strategy with respect to Rusal. Options under consideration include the possibility of carving out Rusal’s international business.” The plan was at “a preliminary stage” and the company will talk further to regulators and key stakeholders, the statement said. Barker will continue to chair the group for a “short period” before handing over to Christopher Bancroft Burnham, the company’s senior independent director. Burnham is a US national who lists a Kaliningrad correspondence address with Companies House. EN+ and Barker were approached for comment.