Former prime minister David Cameron and Australian financier Lex Greensill both face questions from MPs next week, amid ongoing concerns about lobbying.
Mr Greensill - who has yet to comment on the controversy - appears before the Treasury committee on Tuesday.
Mr Cameron will face MPs on the same committee two days later.
The committee is investigating the collapse of Mr Greensill's firm and Mr Cameron's role in trying to access government funding.
Mr Cameron's lobbying for Greensill Capital - which included sending text messages to Chancellor Rishi Sunak - have prompted a review by lawyer Nigel Boardman, ordered by Prime Minister Boris Johnson.
The collapse of Greensill - which filed for insolvency in March - has threatened thousands of UK jobs at Liberty Steel, which was dependent on it for its financing.
Treasury committee chairman, Conservative MP Mel Stride, said: "The committee is determined to answer the key question as to whether HM Treasury responded appropriately to the lobbying on behalf of Greensill Capital, including that carried out by David Cameron."