David Cameron and Rishi Sunak could be called before MPs to answer questions about the former prime minister’s lobbying activities for Greensill Capital.
The Commons Treasury Committee will seek to question the pair after it emerged Mr Cameron sent text messages to the Chancellor as he sought to gain access to Government-backed coronavirus loans for Greensill.
The cross-party panel of MPs also want to question Lex Greensill, the boss of the firm which collapsed into administration in March.
The Bank of England, Financial Conduct Authority and UK Government Investments will also face questions in the probe into the failure of Greensill and its attempts to lobby the Government.
Treasury Committee chairman Mel Stride said: “There are questions to be answered in relation to Greensill Capital regarding the operation of the UK’s financial system and its regulation.
“Also, whether the Treasury responded appropriately to lobbying from Greensill during the pandemic.
“I will be writing shortly to the Chancellor, the Governor of the Bank of England, chief executive of the FCA, and David Cameron requesting answers to various initial questions.
“The Committee will be holding its first evidence session into Greensill Capital next week.”
A series of investigations have now been launched into the role Mr Cameron played in securing Whitehall access for Mr Greensill, whose firm’s collapse now risks thousands of jobs, particularly in the steel sector.
The Commons Public Administration and Constitutional Affairs Committee gave details of its investigation into the lobbying row, which will look at whether existing rules and penalties are tough enough.
The terms of reference published by the committee note the collapse of Greensill Capital and revelations about its relationship with ministers and Whitehall “have raised significant concerns about the propriety of governance in this country” which “risks undermining public trust”.
Committee chairman William Wragg MP said: “Standards in public life are vitally important, and I think most politicians and civil servants fulfil their roles honourably.
“Maintaining and defending that honourable position matters – that’s precisely why this affair has to be scrutinised.
“We will look into whether the rules need tightening up and clarifying and we will make any necessary recommendations without fear or favour.”
The MPs will examine whether codes of conduct for ministers, special advisers and officials are effective, how conflicts of interest are managed and whether the business appointment rules are broad enough.
The committee will also examine how lobbying should be regulated and consider the issues around the use of consultants and contractors in government.
Meanwhile, Boris Johnson sought to play down the extent of links between Whitehall and the private sector, insisting there are not “loads of people” working as civil servants while also employed by a business.
The Prime Minister has asked lawyer Nigel Boardman to investigate after it emerged that former government procurement chief Bill Crothers worked as an adviser for Greensill Capital while in his Whitehall job.
Greensill, which collapsed in March, also employed former prime minister Mr Cameron, who lobbied ministers on behalf of the firm.
Mr Johnson, who said he has had no recent contact with Mr Cameron, said Mr Boardman will look at “the whole thing”.
The Prime Minister told reporters on a campaign visit to Gloucestershire: “I just want to stress one thing to people who are sort of vaguely tuning in to this.
“People should not, in my view, form the impression that the upper echelons of the British Civil Service have got loads of people who are double-hatting, as it were, doing two jobs – it just isn’t true.
“We’ve got one of the best civil services in the world.
“They are fantastically hard-working people, they have been doing an amazing job throughout this Covid pandemic, apart from anything else, and I just wouldn’t want people to get that impression.
“It is simply not the case.”
Cabinet Secretary Simon Case last week ordered Whitehall department chiefs to declare any instances of senior officials performing dual roles outside the Civil Service.