David Cameron’s lobbying of government has drawn fresh criticism after it emerged Rishi Sunak “pushed” officials to explore an alternative plan that could have helped a firm the ex-PM was working for.

Labour, the Lib Dems and the SNP have seized on text messages sent by the chancellor to Cameron that they say expose “Tory cronyism” and raise questions over Sunak breaking the ministerial code.

The two texts, released on Thursday following a Freedom of Information request, relate to the ex-Tory leader’s efforts to secure rescue funding for finance company Greensill Capital.

The firm, which Cameron had been working for since 2018, filed for insolvency after failing to secure support through the government’s Covid Corporate Financing Facility (CCFF).

Greensill Capital’s demise rendered Cameron’s reported tens of millions of share options worthless.

The first message from Sunak to Cameron, sent on April 3 2020, read: “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.”

The second message from Sunak sent on April 23 said: “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 “Charles” refers to Charles Roxburgh, the second most senior civil servant at the Treasury.

But texts from the former prime minister sent to the chancellor were not published as his status as an employee of Greensill Capital meant he had “an expectation of confidence”, it was claimed. 

The Treasury response to the FOI request said: “We are withholding the communications sent by David Cameron to the chancellor. These communications were made by David Cameron in his capacity as an employee of Greensill, and with an expectation of confidence.”

Sunak also confirmed Cameron lobbied three ministers, including himself, over the matter of Greensill Capital’s access to the Covid support scheme.

In a letter sent to shadow chancellor Anneliese Dodds on Thursday, Sunak wrote: “I can confirm that David Cameron reached out informally by telephone to me, and to the economic secretary and the financial secretary, on the matter of Greensill Capital’s access to the CCFF.

“The matter was referred to the relevant officials and, following appropriate consultations as outlined in the previous requests, the request was turned down.

“During this process, this was communicated to Greensill Capital by officials and, in parallel, by me to David Cameron.”

Following the release, Labour’s Dodds said: “These messages raise very serious questions about whether the chancellor may have broken the ministerial code. They suggest that Greensill Capital got accelerated treatment and access to officials, and that the Chancellor ‘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.”

The SNP’s cabinet office spokesperson Stewart Hosie said: “Boris Johnson’s Tory government is stumbling from one scandal to the next. The latest developments around Greensill Capital and access to government departments granted to firms with close links to the Tory party has only raised further questions.

“Tory ministers and former prime ministers casually texting each other over government access utterly reeks.

“When MPs return from recess, Rishi Sunak must come before parliament and set the record straight over his full exchange with David Cameron and what the outcome of those messages were.”

A Liberal Democrat Treasury spokesperson said: “There are now serious questions that the Chancellor must answer about the nature of these conversations. Yet again, the stench of cronyism emanates from this government.

“We need full transparency on exactly what the chancellor did and what David Cameron’s involvement was in persuading him.”