Almost a quarter of MPs calling for a review into the parliamentary sleaze watchdog have previously been found to have broken rules after being investigated by the regulator.

Fifty-nine MPs have backed an amendment that would reject a decision by the Committee on Standards, a cross-party group of MPs, to suspend Conservative MP Owen Paterson for breaching lobbying rules.

Among those who supported Paterson are Conservative MP Richard Drax, who failed to declare a grouse moor, and Tory MP David Morris, who asked questions in Parliament about a firm he had received a £10,000 donation from.

The committee, which is chaired by Labour MP Chris Bryant and includes four Conservative MPs, found that Paterson used his position as an MP to benefit two firms that paid him more than £100,000 a year in total as a consultant.

It justified the suspension on the grounds that “no previous case of paid advocacy has seen so many breaches or such a clear pattern of behaviour in failing to separate private and public interests”. Penalties imposed by the standards committee are usually approved as a formality.

But an amendment tabled by Conservative MP Andrea Leadsom, which was eventually passed by 250 votes to 232, called for the creation of a new committee that would consider whether to review Paterson’s case as well as changes to the current system, which regulates MPs’ conduct.

Angela Rayner, the deputy Labour leader, standing in for Keir Starmer, who has coronavirus, said the Tories “are wallowing in sleaze”.

“In no other profession in our country could someone be found guilty by an independent process and just have their mates vote them back into the job,” she said.

“If it was a police officer, a teacher, a doctor, we would expect the independent process to be followed and not changed after the verdict. It is one rule for them and one rule for the rest of us.”

The proposed committee would be chaired by John Whittingdale, the Tory former culture secretary, and would include four other Conservative MPs, three Labour MPs and one SNP MP, the motion says. Whittingdale would be given a casting vote in the event of a tie, effectively giving the committee a Tory majority.

The ex-minister was himself found to have broken the rules in 2016 after the standards watchdog ruled he did not properly register a £1,500 trip to Amsterdam with his girlfriend.

Fourteen of the MPs backing the amendment have previously breached the code of conduct for MPs. Among them is Tory MP David Morris, who asked questions in Parliament about Aquind, a company owned by Conservative donor Alexander Temerko, after he had received a £10,000 donation.

Kathryn Stone, the parliamentary commissioner for standards said that during her investigation, Morris repeatedly questioned her remit and her right to consult other officials. Morris later apologised to the commissioner for his behaviour.

Other backers include Conservative MP Craig Mackinlay, who failed to declare shares in an airline on the member's register of interest in 2015. (The airline never traded and the shares had only a nominal value.)

One of the supporters, Conservative MP Karl McCartney was found to have breached the rules three times last month by failing to properly declare his links to a family firm, Moonlighting Systems.

At today’s Prime Minister’s Questions, Boris Johnson defended his decision to whip Conservative MPs to back the amendment, saying the complaints process was flawed for not allowing the former minister a right of appeal.

Currently, allegations of misconduct are first investigated by the independent parliamentary commissioner for standards before being reviewed by the standards committee.

The calls to rescind Paterson’s suspension come just days after a report by parliament’s ethics body found that MPs are “not effectively regulated” by the current system. It recommended that ministers and officials should face tougher sanctions, including fines and resignations, for misconduct.

Kevin Barron, a former Labour MP and chair of the standards committee, said that the amendment was a “backwards step for accountability”.

“Parliament has made good progress on accountability over the last decade, the government amendment would destroy all that progress,” he wrote on Twitter.

Correction, 6 November: This article has been updated to reflect the fact that Craig Mackinlay breached the rules by failing to declare that he owned more than 15% of an airline company's shares but the company never traded and the shares had only a nominal value.