The exchange of messages between the pair took place last year when Cameron served as an adviser for the financial services company, Greensill Capital, found in the middle of an ongoing lobbying row.

Cameron lobbied the government on behalf of Greensill Capital in order to secure the company’s access to a Bank of England loan scheme meant to put off pressure from businesses amid the pandemic. A few months later the company collapsed.

The Treasury revealed the text of the messages sent by Sunak to Cameron but withheld Cameron’s messages as they were made “in his capacity as an employee of Greensill, and with an expectation of confidence.”

In response to the former PM, the Chancellor said the following in the two texts on 3 April and 23 April 2020.

"Hi David, thanks for your message. I am stuck back to back on calls but will try you later this evening and if gets too late, first thing tomorrow. Best, Rishi"

"Hi David, apologies for the delay. I think the proposals in the end did require a change to the Market Notice but I have pushed the team to explore an alternative with the Bank that might work. No guarantees, but the Bank are currently looking at it and Charles should be in touch. Best, Rishi"

The government confirmed that Cameron had also reached out to the Economic Secretary John Glen and the Financial Secretary Jesse Norman on the matter of Greensill’s access to the Covid Corporate Financing Facility (CCFF).

According to the Treasury, the matter was referred to “relevant officials and, following appropriate consultations” the request lobbied by Cameron was turned down.

The Labour Shadow Chancellor, Anneliese Dodds MP, however, argued that Sunak’s messages suggested that he “pushed” officials to consider Greensill’s requests.

“The Chancellor’s decision to open the door to Greensill Capital has put public money at risk. There must be a full, transparent and thorough investigation into the chain of events that saw Greensill awarded lucrative contracts, the freedom of Whitehall and the right to lend millions of pounds of government-backed Covid loans,” Dodds said in a statement.

Greensill Capital - a key financial backer of Britain’s third-largest steelmaker Liberty Steel - went into administration on 8 March, 2020, leaving thousands unemployed.