A new inquiry will be launched into civil servants taking second jobs, likely leading to officials facing tougher scrutiny after the Greensill scandal, the Guardian has learned. Simon Case, the cabinet secretary, is due to announce the move at his appearance in front of a parliamentary committee on Monday, after an audit of how widespread the problem is across Whitehall. Permanent secretaries at each department were instructed to find out how many mandarins held positions outside the civil service, when it was discovered that lobbying on behalf of Greensill Capital extended beyond just David Cameron and other politicians’ involvement. The Guardian revealed weeks ago that official approval was given for Bill Crothers to begin advising Greensill in September 2015 while still employed in the civil service. He denied any wrongdoing and said such outside roles were “not uncommon”. While the government has set up an independent review led by Nigel Boardman to examine how ministers dealt with Cameron’s advances, Case is now launching his own review. A source said it would examine “the second job issue within the civil service” and be announced formally on Monday. Case is facing the public administration and constitutional affairs committee for a rare public grilling on Monday afternoon. He is likely to be asked for the findings of his audit and what reforms he intends to make to the existing rules on what other roles impartial civil servants can have. Currently the civil service management code states that: “Departments and agencies must require staff to seek permission before accepting any outside employment which might affect their work either directly or indirectly, and must make appropriate arrangements, which reflect the business appointments rules for civil servants … and any local needs, for the handling of such requests.” However there is concern the relevant section of the code is too loosely worded. Case is understood to have raised concerns at a meeting last week and suggested there should be more scrutiny by officials when signing off double jobs. The lobbying issue – which Cameron himself warned in 2010 was “the next big scandal waiting to happen” – exploded recently after it was revealed Greensill was attempting to lobby for access to the government’s largest Covid-support scheme, the Covid corporate financing facility (CCFF), which the company ultimately did not quality for. Cameron, who was a special adviser to the company’s board and partly paid in share options, was found to have sent texts and emails to ministers as he sought approval for policies that would benefit the lender. It has since emerged that the former prime minister personally lobbied the Treasury’s most senior civil servant, Sir Tom Scholar, via text message and secured nine meetings with another of the department’s key officials. Cameron also lobbied John Glen MP, the economic secretary to the Treasury. In correspondents released by the Treasury last week copied into top officials, Cameron is said to have argued that supporting Greensill would be “the most effective” way to help the small and medium businesses that relied on it for finance. Greensill also hired another Cabinet Office adviser – former Morgan Stanley banker David Brierwood. He was brought into the heart of government during Cameron’s administration in 2014, the same year Greensill’s founder Lex Greensill apparently took on a similar role. Two months later, Brierwood was recruited to join Greensill Capital’s board as a director. Brierwood remained a Greensill director throughout the rest of his Whitehall appointment, which lasted more than three and a half years, according to his LinkedIn profile, which also showed that he resigned from the supply chain finance firm in February this year. Eight separate inquiries have since been launched into the lobbying issues thrown up by Greensill, including Boardman’s, three by select committees, the National Audit Office, as well as the committee on standards in public life. Cameron released a statement two weeks ago after a long period of silence, saying he had reflected on his conduct and accepted that he should have communicated “through only the most formal of channels” and there were “important lessons” to be learned. His spokesperson issued another statement later, confirming Cameron welcomed the Boardman inquiry “and will be glad to take part”. Cameron has previously denied wrongdoing, saying: “In my representations to government, I was breaking no codes of conduct and no government rules. The registrar of consultant lobbyists has found that my activities did not fall within the criteria that require registration.”