David Cameron accepts it was a mistake to lobby Chancellor Rishi Sunak with private text messages over access for his employer to a coronavirus loan scheme, according to allies.

The former prime minister is continuing to face questions over his efforts to secure access for finance company Greensill Capital, the collapse of which has put thousands of UK jobs at risk.

This week it emerged the Chancellor responded to texts from Mr Cameron saying he had “pushed” officials to consider plans that could have helped Greensill in 2020.

Mr Cameron is yet to comment publicly on the controversy or the collapse of the firm last month, but friends of the Conservative former leader have spoken to the Financial Times about his involvement.

“I think he would agree it could be argued that a formal letter would have been more appropriate,” one ally told the newspaper.

Questions have also arisen about the privileged access the firm’s founder Lex Greensill had across Government while Mr Cameron was in No 10, and how the Australian financier was able to benefit from a Government loan scheme he advocated.

A business card from Mr Greensill saw him titled as a “senior adviser, Prime Minister’s office” and was complete with a personal No 10 email address.

Friends sought to downplay the amount to which Mr Cameron saw Mr Greensill while in office.

“David thinks he met him once in the entirety of his time as prime minister,” one said, suggesting this was in October 2012.

But in 2014 the then prime minister pointed out Mr Greensill in the audience of a speech to the Federation of Small Businesses when questioned on banking.

“I’ve got my top team from the No 10 policy unit sitting here. We’ve also got Lex Greensill – Lex, where are you? Give us a wave,” Mr Cameron said.

“Lex is sorting out the whole supply chain finance issue for us.”

After leaving Downing Street, Mr Cameron went to work as an advisor for Greensill and lobbied ministers for support through the Government’s corporate Covid finance scheme.

In response to a Freedom of Information request, the Treasury published two responses from the Chancellor to Mr Cameron.

“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,” Mr Sunak wrote, in April.

Ultimately Mr Cameron’s efforts failed and Greensill filed for insolvency.

The move has put thousands of steelmaking jobs in the UK at risk and rendered Mr Cameron’s reported tens of millions of share options worthless. Greensill was the main financial backer of Liberty Steel.

Labour’s shadow chancellor Anneliese Dodds said the text messages “raise very serious questions” on whether Mr Sunak broke the ministerial code.

She also argued the Chancellor’s actions “put public money at risk”, and demanded a full investigation.