A failed financier at the centre of a Downing Street lobbying scandal had no contract to work for the government despite spending years inside No 10 under David Cameron, a committee of MPs has been told. Lex Greensill had a desk and a security pass to gain access to the prime minister’s offices, senior civil servants told MPs. But officials disclosed on Monday that he was neither a civil servant nor a special adviser and they could find no contracts for Greensill’s three years in Whitehall. Appearing before the public administration and constitutional affairs committee on Monday, Simon Case, the cabinet secretary, said he was surprised and puzzled by the lack of paperwork. “We cannot explain how these decisions were taken or why … it does not look appropriate,” he said. This will form part of an independent inquiry conducted by the corporate lawyer Nigel Boardman. The government has come under mounting pressure to explain why Greensill was allowed to become an unpaid adviser to government under Cameron – a role in which he was reportedly allowed to pitch his financial projects across Whitehall. His business card described him as a senior adviser to the prime minister’s office. His firm Greensill Capital collapsed into administration last month leaving thousands of jobs in the balance. Cameron and Greensill are under investigation for lobbying ministers for access to government schemes as recently as last year. Cameron had pushed the Bank of England and the Treasury to risk up to £20bn in taxpayer cash to help Greensill Capital during March and April 2020, as the lender started to face “significant” financial pressure at the start of the Covid pandemic. Darren Tierney, the director general of propriety and ethics in the Cabinet Office, told the committee that Lex Greensill’s role as an adviser was “unclear”. “He wasn’t a special adviser – his exact status is unclear. That’s one of the things that we have asked Nigel Boardman to look into,” he said. “He was appointed as an unpaid adviser on supply chain finance in January 2012. He did that until 2015. In 2013, he also became a crown representative, which lasted until 2016, when he left the Cabinet Office.” Greensill had a security pass for the Cabinet Office and Downing Street, Tierney said. He was given security clearance several months after his appointment. Case said although Greensill had access to Downing Street, it is unclear whether he was working there or what he did because they could find no relevant contract. “I can’t explain the Greensill case,” he said. Asked if there is a conflict of interest, Case added: “We can’t explain. It looks like there were conflicts and we’re not clear on how they were managed. From our cursory look, we can’t see the evidence … That doesn’t look right.” The Labour MP Lloyd Russell-Moyle asked: “Do you think it’s acceptable that there are effectively some people advising government, however small numbers, there is no record of that you can easily get to and seem to be covered by no guidelines and standards?” Case said: “For me, I can’t explain the Greensill case … I don’t think it’s acceptable. I don’t believe it is a common practice. I certainly don’t think there’s anything happening at the moment that is the equivalent.” Greensill’s reappointment letters would have been signed off by Francis Maude, the then Cabinet Office minister, Tierney said. Lord Maude is reviewing the Cabinet Office’s functions for Boris Johnson’s government. MPs also asked why Bill Crothers, a senior civil servant in charge of government procurement, had been allowed to work for Greensill while keeping his job in Whitehall. Tierney said emails suggested Crothers’ appointment at Greensill had been approved because the bank had not had any public-sector work at the time. He confirmed the Guardian’s previous disclosure that Crothers’ second job had been signed off by John Manzoni, the former Cabinet Office permanent secretary, as well as Jeremy Heywood, the then cabinet secretary. Maude brought Crothers into the Cabinet Office in 2012.