(Bloomberg) --

U.K. cabinet minister Jacob Rees-Mogg is being investigated by Parliament’s standards commissioner over an alleged breach of rules relating to outside employment and earnings.

Kathryn Stone is looking into whether Rees-Mogg, who runs the parliamentary agenda for the government, breached the code of conduct for MPs, according to her office website. The exact nature of the complaint has not been made public, but the probe follows complaints from the opposition Labour party that Rees-Mogg apparently failed to declare he’d received 6 million pounds ($8 million) in loans from one of his companies.

The announcement is a blow for Prime Minister Boris Johnson who is trying to put an intense row over ethics behind him. Johnson has faced a backlash from his own party and the public since making a botched attempt to protect a former minister from sanction over paid lobbying.

Scottish Tory leader Douglas Ross is also under investigation by Stone in relation to his financial interests, according to the commissioner’s website.

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