Commons Leader Jacob Rees-Mogg and Scottish Conservative leader Douglas Ross have become the latest MPs to face a standards probe.
On Wednesday, both were added to the list of MPs that are under investigation by Parliamentary Commissioner for Standards Kathryn Stone.
The decision to investigate Mr Rees-Mogg comes after Labour demanded an investigation into a £6 million loan that the party said he did not declare properly.
Last month, the opposition party called for Ms Stone to follow-up on claims in the Mail On Sunday that the Cabinet minister failed to declare director’s loans from his company Saliston Limited between 2018 and 2020.
Mr Rees-Mogg’s opposite number, shadow Commons leader Thangam Debbonaire, said there appeared to have been “yet another egregious breach of the rules” after the emergence of the report.
Labour deputy leader Angela Rayner separately wrote to the independent adviser on ministers’ interests, Lord Geidt, over the loans.
In her letter, Mr Rayner said that failing to declare director’s loans worth £2.94 million a year “allowed Mr Rees-Mogg to borrow a large sum of money at a very low interest rate” and argued that it “should have been declared”.
Mr Rees-Mogg said the rules did not dictate that loans be declared.
Meanwhile, Mr Ross revealed last month that he had referred himself to the commissioner after failing to declare thousands of pounds in outside earnings.
According to reports in The Herald, the MP failed to declare £28,218.57 in earnings from his second job as an MSP and third job as a football referee.
The undeclared income includes £6,728.57 from 16 football matches in 2021 and 2020, and £21,490 in a top-up salary from his role as an MSP.
Speaking to the Herald, Mr Ross said: “Since realising my mistake last week, I contacted the Office of the Register of Interests and made them aware of the situation.
“All payments have now been declared, including those from my MSP salary that are donated to charities.”
The commissioner does not confirm what claims she is investigating once a probe has been declared.
According to the commissioner’s website, Mr Rees-Mogg and Mr Ross are both being investigated over “registration of an interest under category one of the Guide to the Rules (Employment and Earnings)”, and it refers to paragraph 14 of the Code of Conduct.
The relevant paragraph in the code states: “Members shall fulfil conscientiously the requirements of the House in respect of the registration of interests in the register of members’ financial interests.
“They shall always be open and frank in drawing attention to any relevant interest in any proceeding of the House or its committees, and in any communications with ministers, members, public officials or public office holders.”
In a statement, Mr Rees-Mogg said: “Saliston is 100% owned by me and this is declared clearly in the Commons register and to the Cabinet Office.
“It has no activities that interact with Government policy.
“The loans from 2018 were primarily taken out for the purchase and refurbishment of 7 Cowley Street as temporary cash flow measures.
“All loans have either been repaid with interest, in accordance with HMRC rules, or paid as dividends and taxed accordingly.
“The register asks for earnings, not loans, which is why I was declared an as a non-remunerated director until I resigned on entering Government.
“Loans are not earnings and are not declarable in the register of interests.”