GORDON Brown has said former ministers and prime ministers should 'never be lobbying' the government for commercial gain.

The former Labour Prime Minister was speaking this morning following revelations that David Cameron lobbied the Treasury on behalf of scandal-hit finance firm Greensill Capital.

After weeks of speculation and mounting pressure on the former Conservative PM, Mr Cameron issued a statement last night and broke his silence about his activities.

Mr Cameron said there were "important lessons to be learnt" from the incident, which saw him lobby Rishi Sunak, and set up a private drink between Lex Greensill and health Secretary Matt Hancock.

Labour has called on the former PM to appear in Parliament to answer "many serious questions" over his behaviour.

Speaking on Radio 4's Today programme this morning, Mr Brown said former prime ministers or ministers should not be "lobbying for commercial purposes" and said to do so was bringing public service "into disrepute".

He also suggested that a change in law may be required to address such activities.

He said: "I can’t comment on the individual detail of this but for me there are principles about public service – it cannot ever become a platform for private gain.

"Ministers must never be lobbying, former ministers, prime ministers, must never be lobbying for commercial purposes. Current ministers should not be entertaining such lobbying.

"If we can’t succeed in achieving this stopping by the sort of flexibility of the rules, we are going to have to pass laws to make sure that at least for, say, five years, no serving or former prime minister or minister is ever lobbying for any commercial purpose within government.

"It simply brings public service into disrepute.”

Mr Cameron, who served as PM between 2010 and 2016 released a statement last night saying: “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 get Greensill’s proposals included in 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.”

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.

It comes after it emerged the Chancellor responded to the numerous 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 also described the decision to exclude his employer’s firm 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.

Labour’s shadow chancellor of the Duchy of Lancaster Rachel Reeves said: “Many serious questions remain unanswered and it is crucial that the former prime minister appears before Parliament so that all the information is brought to light.

“Transparency and accountability are crucial and that requires the utmost openness from government to establish the full facts behind this scandal.”