Calls for an investigation have been made after Rishi Sunak revealed he “pushed” officials to consider plans that could have helped a firm David Cameron was lobbying for.

Labour also questioned whether the Chancellor had broken the ministerial code, while the SNP urged Mr Sunak to appear before Parliament next week to “set the record straight” over his full exchanges with Mr Cameron.

Mr Sunak had said the former prime minister “reached out informally by telephone” to him, as well as Economic Secretary John Glen and Financial Secretary Jesse Norman, over Covid support for the collapsed finance company Greensill Capital.

Greensill had approached Treasury officials regarding access to the Covid Corporate Finance Facility (CCFF), administered by the Bank of England.

The Chancellor was defended by Transport Secretary Grant Shapps on Friday, who insisted that Mr Sunak followed the ministerial code “absolutely to the letter”.

Mr Sunak said the meetings covered requests made by Greensill to change the terms of the scheme or broaden its scope to allow them access to it, both of which were rejected.

Greensill subsequently filed for insolvency, putting at risk thousands of steelmaking jobs in the UK and rendering Mr Cameron’s reported tens of millions of share options worthless.

The Chancellor defended the decision to listen to the requests given the desire to help businesses survive the Covid-19 pandemic, before confirming Mr Cameron’s lobbying activities.

Mr Sunak also published two text messages he sent to Mr Cameron in April 2020, although messages sent by Mr Cameron have been withheld by the Government.

The Treasury, responding to a Freedom of Information request, said: “These communications were made by David Cameron in his capacity as an employee of Greensill, and with an expectation of confidence.”

The first message from Mr Sunak to Mr 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.”

I don’t think there is any issue here of impropriety at all

The second message from Mr 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 Treasury also published messages sent to and from its second permanent secretary, Charles Roxburgh.

Asked if Mr Sunak had behaved appropriately, Mr Shapps told BBC Radio 4’s Today programme: “I don’t think there is any issue here of impropriety at all.

“He has followed absolutely to the letter what you should do. It actually says in the ministerial code, if you get contact like this, what you must do is forward it on and let it be dealt with via the usual channels.

“Which is exactly what happened, to a negative result.”

On whether Mr Cameron had behaved appropriately, Mr Shapps said: “A private citizen can work with who they want and do what they like.

“If you have been in Government, you have to wait two years or get permission – it’s been much longer than two years in David Cameron’s case.

“There is a slight irony that he predicted all of this ten years ago and said he thought that this may be an issue, but he’s a free man, he’s an individual, he can work in business or do whatever else he likes.”

Mr Sunak, in a letter sent to shadow chancellor Anneliese Dodds on Thursday, explained Greensill’s requests to change the CCFF.

He then 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.”

Ms 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.”

SNP Cabinet Office spokesman Stewart Hosie said Boris Johnson’s Government is “stumbling from one scandal to the next”, adding: “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.”

Mr Cameron has been exonerated by a watchdog over the issue.

The Registrar of Consultant Lobbyists concluded Mr Cameron was an employee of Greensill so was not required to declare himself on the register of consultant lobbyists.