David Cameron is at the centre of an unprecedented formal inquiry after Boris Johnson ordered a probe into lobbying by the former prime minister on behalf of the collapsed company Greensill Capital. The independent investigation will examine the firm’s role in government, supply chain financing and communications by employees, including Cameron, who joined Greensill as an adviser in 2018, two years after resigning as prime minister, and who stood to make millions of pounds from his role. It is understood that the inquiry will also have licence to recommend changes to lobbying regulations. Government sources stressed that the decision on Monday was not a personal attack by Boris Johnson on his old rival, as it will be seen by some allies of Cameron, but said it was clear that the public deserved a transparent explanation of the scandal. Cameron broke his month-long silence on Sunday night with a 1,700-word statement after a slew of damaging stories about his lobbying efforts on behalf of Greensill, including messages to the chancellor, Rishi Sunak, two junior ministers, senior civil servants and a No 10 special adviser. He said 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. On Monday night his spokesperson issued a statement saying Cameron welcomed the inquiry “and will be glad to take part”. Campaigners including Transparency International have said the saga “highlights deep flaws in the UK’s approach” and that an inquiry should cover the lack of transparency in lobbying, enforcing the ministerial code and the revolving door between government and the private sector. The group said ministerial meetings that are meant to be reported are often left unpublished and unpoliced and have called for a change in the direction of the US, Canada, Ireland and Scotland, where attempts to influence ministers must be reported by lobbyists themselves. The independent review will be led by Nigel Boardman, a corporate lawyer with experience of government inquiries and a non-executive board member of the Department for Business, Energy and Industrial Strategy (BEIS). Boardman is a senior consultant at Slaughter and May, a multinational law firm that previously challenged the Cameron administration when the then prime minister proposed to change lobbying rules. In a 2013 submission to a committee on standards in public life consultation, the City of London Law Society, which represents the firm and others, suggested that adopting a blanket statutory register of lobbyists “may have the effect of stifling productive, even essential, dialogue between legislators and those who consider the implications and practicalities of relevant legislation on a day-to-day basis”. Boardman was a partner with Slaughter and May at the time. He left that post in 2019 and while still a senior consultant at the firm, is understood to be acting on an individual basis on the lobbying review. He ran a review for the Cabinet Office last year on procurement, after the controversy over the awarding of government contracts during the early weeks of the coronavirus pandemic. Rachel Reeves, shadow chancellor of the duchy of Lancaster, said: “This is a government mired in cronyism and scandal. It’s not good enough for the Conservatives to appoint an inquiry head from an organisation that lobbied to limit the scope of the register, then carry out an inquiry policing themselves and expect everyone to just look the other way.” The new inquiry – the like of which has never been launched in relation to a former prime minister – will also look at the development and use of supply chain finance, offered by Greensill, and its associated activities in government. Some eyebrows have been raised among MPs about Johnson launching a review into Cameron, described by one veteran Tory MP, tongue-in-cheek, as “the hardest decision he must have had to make”. Johnson’s official spokesman said there was “significant interest in this matter, so the prime minister has called for the review to ensure government is completely transparent about such activities, and that the public can see for themselves if good value was secured for taxpayers’ money”. It is understood that the review will look at Cameron’s lobbying after his time in government. No 10 said it “will also look at how contracts were secured and how business representatives engaged with government”. Downing Street did not set out a timescale, but said it would be expected to report relatively quickly. “The prime minister wants this to be done thoroughly and he wanted it to be done promptly, so you can expect a prompt return on this,” his spokesman said. Chris Bryant, the Labour MP who chairs the committee on standards in public life, said he believed there should be a “full inquiry into lobbying”. “My personal experience is that sometimes lobbying can be helpful – when I was on the mental health bill committee, the information I got from the BMA, mental health charities and some pharmaceutical companies meant I got a lot of good information. What matters is transparency,” he said. Bryant said a joint committee of inquiry in the Lords and the Commons, including the standards committee, the public administration and constitutional affairs committee and the BEIS committee, could look at all aspects of lobbying. Many Conservative MPs have shown little appetite for parliamentary inquiries into Cameron and Greensill, meaning some committees are blocked from launching them because of Tory majorities. However, Bernard Jenkin, the Tory MP who chairs the powerful liaison committee, backed the Greensill inquiry and changes to the ministers’ code of conduct to force them to declare conversations about possible employment after their time in government. Jenkin said the issue should be looked at immediately by the new adviser on ministerial interests. Johnson is yet to replace Sir Alex Allan, who quit before Christmas after the prime minister backed the home secretary, Priti Patel, despite a highly critical report into bullying. Slaughter and May has been approached for comment.