The former prime minister was revealed to have made $4.5m (£3.25m) after cashing in shares from the company in 2019, and a salary of roughly $1m a year for work as a part-time adviser.
The BBC’s Panorama programme has reportedly obtained a letter between the firm and the former prime minister detailing the value of his shares.
Mr Cameron is believed to have made about $10m before tax from Greensill over a two-and-a-half year period.
His spokesman said the former PM did not receive “anything like” the sums reported by the BBC, and added he “deeply regrets” Greensill’s collapse.
Mr Cameron began his role as an adviser to Greensill in August 2018, just over two years after he resigned as prime minister in July 2016.
The firm’s founder, Lex Greensill, advised the Government during Mr Cameron’s time in No.10, but he denied he had been offered a role while in office.
Greensill provided so-called supply chain finance to businesses, which meant the finance firm would pay a company’s invoice immediately after it was sent, cutting out the usual delay that can restrict companies’ cash flows.
The firm was the main financial backer to GFG Alliance – a group of companies controlled by the steel magnate Sanjeev Gupta, which borrowed around $5 billion from Greensill.
But Greensill used its own cash to cover repayments GFG could not afford, according to Panorama.
Mr Cameron lobbied the UK Government to act as a new investor for the firm, texting ministers including Chancellor Rishi Sunak, as well as Boris Johnson’s senior adviser Sheridan Westlake, and deputy Bank of England governor Sir Jon Cunliffe.
The Bank of England turned Greensill down, but in June 2020 Greensill was approved as a lender under a government scheme designed to get emergency cash to companies affected by the Covid pandemic.
Greensill collapsed in March 2021, leading to a series of inquiries into Mr Cameron’s conduct.
Mr Cameron’s spokesman said: “David Cameron did not receive anything like the figures quoted by Panorama.”
The spokesman added: “David Cameron deeply regrets that Greensill went into administration and is desperately sorry for those who have lost their jobs.
“As he was neither a director of the company, nor involved in any lending decisions, he has no special insight into what ultimately happened.
“He acted in good faith at all times and there was no wrongdoing in any of the actions he took. He made the representations he did to the UK Government, not just because he thought it would benefit the company, but because he sincerely believed there would be a material benefit for UK businesses at a challenging time.
“He had no idea until December 2020 that the company was in danger of failure.”
The spokesman also said: “David Cameron has been clear all along that there are important lessons to be learnt from this whole episode and, as such, he has been pleased to provide evidence to the Government’s Boardman Inquiry, and to two Parliamentary Select Committees.”
Labour’s deputy leader Angela Rayner said it was “ludicrous” that Mr Cameron “walked away with $10m for two-and-a-half years’ part-time work for a company that collapsed, risking thousands of pounds of taxpayers’ money”.