An investigation has been launched by Westminster’s standards watchdog into Douglas Ross.
It comes after it emerged he failed to declare thousands of pounds in outside earnings while serving as an MP.
Last month, Ross said he was “deeply sorry” and admitted he had made a “huge mistake”, having also referred himself to the Parliamentary Commissioner for Standards Kathryn Stone.
The Herald newspaper reported that Ross had failed to declare £28,218.57 in outside earnings from his second job as an MSP and third job as a football referee.
After he realised his mistake, Ross explained, he contacted the Office of the Register of Interests and made them aware of the situation.
He added that all payments had now been declared, including those from his MSP salary which are donated to charities.
Commons Leader Jacob Rees-Mogg is also set to be investigated by the Commissioner.
Labour had previously demanded an investigation into a £6m loan they said the MP did not declare properly.
The commissioner does not confirm what claims she is investigating once a probe has been declared.
According to the commissioner’s website, Rees-Mogg and 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.”