A spokesperson for Tory chief whip Simon Hart said that following his self-referral to the Parliamentary Commissioner for Standards, Mr Benton "has had the Conservative Party Whip suspended whilst an investigation is ongoing".

Rishi Sunak, who entered office last year promising "integrity" within the party, had come under pressure to withdraw the whip from the Blackpool South MP.

Labour said the Prime Minister's failure to act before Mr Benton referred himself to the Commissioner showed his "weakness".

Mr Benton was caught on camera telling undercover reporters posing as investors how he was willing to take actions which would break Parliament's lobbying rules.

Under those rules, MPs are forbidden from advocating a particular matter in the House or raising it with ministers in return for payment.

They are also prohibited from serving as a paid parliamentary adviser or consultant or guiding firms on ways to influence Parliament.

In a meeting in early March, Mr Benton described how he could support the fund, which he believed was set up by an Indian businessman looking to make investments in the UK betting and gaming sector, by attempting to water down proposed gambling reforms.

It comes as the Government is carrying out a major review of gambling laws, mulling stricter regulations that could affect operators' profits.

Mr Benton offered a "guarantee" to provide a copy of an upcoming gambling White Paper to the business at least two days before publication, potentially allowing it to benefit from market sensitive information.

He also said he could table parliamentary written questions and that he had previously done so on behalf of another company.

Mr Benton said he could offer "the direct ear of a minister who is actually going to make these decisions" and speak to them outside the Commons voting lobby.

The MP agreed with a fee proposed by the reporters in the range of £2,000 to £4,000 a month for two days' work.

Following the suspension of the whip, which means Mr Benton no longer sits in the Commons as a Tory, a Labour spokesperson said: "Yet again we see Rishi Sunak's weakness. Instead of acting right away, he waited until Scott Benton referred himself to the Commissioner.

"Rishi Sunak's lack of mandate means he's too nervous to act against his own troops. No wonder Tory MPs think they can get away with blue murder."

The party's shadow Commons leader Thangam Debbonaire said Mr Sunak "must get a grip of this new wave of Tory sleaze and take immediate action to stop this shameful cash for questions scandal spiralling even further".

Lib Dem deputy leader Daisy Cooper said: "These shocking revelations are yet another damning indictment of the state of the Conservative Party. The British public are sick of Conservative sleaze."

It comes after former cabinet ministers Matt Hancock and Kwasi Kwarteng drew criticism for offering to advise a bogus South Korean company for up to £10,000 a day in a sting by the campaign group Led By Donkeys last month, although there was no accusation of wrongdoing.

Tory MP Bob Seely told TalkTV: "I hate the way that these rich and powerful interests get themselves embroiled with MPs and we shouldn't be doing it.

"I'm trying to be super careful about this stuff. I wish my colleagues would as well".

In a statement, Mr Benton said: "Last month I was approached by a purported company offering me an expert advisory role. I met with two individuals claiming to represent the company to find out what this role entailed. After this meeting, I was asked to forward my CV and some other personal details. I did not do so as I was concerned that what was being asked of me was not within Parliamentary rules.

"I contacted the Commons Registrar and the Parliamentary Standards Commissioner who clarified these rules for me and had no further contact with the company. I did this before being made aware that the company did not exist and the individuals claiming to represent it were journalists."

Downing Street said it was first and foremost a matter for the Parliamentary Standards Commissioner Daniel Greenberg, and whipping matters were for the Whips Office.

Mr Greenberg's office has been contacted.