Jacob Rees-Mogg faces a Parliament sleaze probe following claims he failed to properly declare £6 million in cheap loans.
The Parliamentary Commissioner for Standards, Kathryne Stone has launched a formal investigation, after it was alleged the Commons leader had failed to properly declare loans to his company.
An update to the Commissioner's website, published today, said Mr Rees-Mogg was under investigation over the 'registration of an interest under Category 1 of the Guide to the Rules' - adding that it was related to 'employment and earnings'.
The site does not specify what the investigation relates to.
But it comes after Labour deputy leader Angela Rayner wrote to the independent adviser on ministers' interests, Lord Geidt, over a series of loans to Mr Rees-Mogg's company Saliston Limited, between 2018 and 2020.
In her letter, revealed by the Mirror last week, she said that failing to declare director's loans worth £2.94m a year "allowed Mr Rees-Mogg to borrow a large sum of money at a very low interest rate".
She added: "The financial benefit to Mr Rees-Mogg in this transaction is the difference in the interest he paid on this loan compared to a loan that he could take out on the open market from another provider, for example a bank.
"In this transaction, this difference is the value of the financial benefit transferred to Mr Rees-Mogg, which is a financial interest that should have been declared."
Mr Rees-Mogg borrowed up to £2.94m a year in "director's loans" from his firm Saliston Ltd between 2018 and 2020.
Although it does not specifically identify director's loans, the MP's code of conduct requires directors to declare "taxable expenses, allowances and benefits".
The Leader of the House of Commons stated that he was an "unremunerated director" and shareholder of the firm but did not mention he had taken out the loans.
By using director's loans he was able to borrow the large sum at very low interest rates.
UK company Saliston Ltd has previously been described as a "holding company" by Mr Rees-Mogg, with £8m property assets, understood to include a Mayfair house.
Saliston also has a stake in asset management firm Somerset Capital Management LLP, which Mr Rees-Mogg co-founded.
He paid just £48,945 interest to Saliston on £6m of loans over three years, a rate of just 0.8%.
The deputy Labour leader and shadow chancellor of the Duchy of Lancaster pointed to a section of the ministerial code which says that "ministers must ensure that no conflict arises, or could reasonably be perceived to arise, between their public duties and their private interests, financial or otherwise".
Downing Street refused to comment on the specifics.
The Prime Minister's press secretary said: "The Leader of the House of Commons has addressed this directly previously but beyond that it's a matter for the Parliamentary Standards Commissioner, which is independent so you wouldn't expect us to comment on it."
