David Cameron has accepted he should have communicated with the Government “through only the most formal of channels” as he acknowledged he made mis-steps over the Greensill Capital lobbying controversy.

Breaking his weeks of silence, the former prime minister said in a statement to the PA news agency that having “reflected on this at length” he accepts there are “important lessons to be learnt”.

The “growing scandal” began after it emerged the Conservative privately lobbied ministers including Chancellor Rishi Sunak for access to an emergency coronavirus loan for his employer, the scandal-hit financier Lex Greensill.

The total number of ministers to be entangled in the controversy reached four when it was reported that Mr Cameron arranged a “private drink” between Health Secretary Matt Hancock and Mr Greensill to discuss a payment scheme later rolled out in the NHS.

Mr Cameron also lobbied a senior Downing Street adviser to rethink Mr Greensill’s application for access to emergency funding.

The former prime minister said on Sunday: “In my representations to Government, I was breaking no codes of conduct and no government rules.”

He said that “ultimately” the outcome of his efforts to win access to the Government’s Covid Corporate Financing Facility (CCFF) was that “they were not taken up”.

“So, I complied with the rules and my interventions did not lead to a change in the Government’s approach to the CCFF,” he added.

“However, I have reflected on this at length. There are important lessons to be learnt. As a former prime minister, I accept that communications with government need to be done through only the most formal of channels, so there can be no room for misinterpretation.”

Questions were mounting over his efforts to secure access for the finance company, which later collapsed, putting thousands of UK steelmaking jobs at risk.

Mr Cameron said that “many of the allegations” made in recent weeks “are not correct” as he challenged what he said is was a “false impression” that Mr Greensill was a key member of his team while in No 10.

He insisted Mr Greensill was “not a political appointee” and had been brought in by the late cabinet secretary Lord Heywood.

“The truth is, I had very little to do with Lex Greensill at this stage – as I recall, I met him twice at most in the entirety of my time as prime minister,” Mr Cameron said.

He also said that the remuneration in shares for Greensill are “nowhere near the amount speculated in the press” after their worth was suggested to be in the dozens of millions.

Mr Cameron sought to defend the use of his profile as a former prime minister to lobby his successors in government on behalf of Greenhill, which hired him as an adviser in August 2018.

“I thought it was right for me to make representations on behalf of a company involved in financing a large number of UK firms. This was at a time of crisis for the UK economy, where everyone was looking for efficient ways to get money to businesses,” Mr Cameron argued.

Mr Cameron also issued a defence of meeting Mohammed bin Salman during a business trip in January 2020, more than a year after the killing of journalist Jamal Khashoggi in October 2018.

As early as the month of the murder, MI6 chief Sir John Sawers said “all the evidence” suggested the prince’s critic had been murdered on the orders of someone close to him.

“While in Saudi Arabia, I took the opportunity to raise concerns about human rights, as I always did when meeting the Saudi leadership when I was Prime Minister,” Mr Cameron said.

Mr Cameron was prime minister between 2010 and 2016 before being hired as an adviser by Greensill in August 2018. Mr Greensill was a Government adviser on finance during Mr Cameron’s time in No 10.

This week, it emerged the Chancellor responded to private texts from Mr Cameron by saying on April 23 last year that he had “pushed” officials to consider plans that could have helped Greensill.

Mr Cameron was said to have described the decision to exclude his employer’s firm, Greensill Capital, from the multibillion-pound scheme as “nuts” in an email to a senior adviser to Prime Minister Boris Johnson and pressed for the Chancellor to reconsider.

“What we need is for Rishi (Sunak) to have a good look at this and ask officials to find a way of making it work,” Mr Cameron emailed on April 3 last year.

Labour called for Mr Sunak to “come out of hiding” and make a statement to Parliament about the “growing scandal”, and reiterated demands for an investigation.

As Mr Cameron pointed out, the Registrar of Consultant Lobbyists cleared him of breaking lobbying rules because as an employee of Greensill he was not required to declare himself on the register.

But the issue has led to calls for an overhaul of lobbying rules.