A formal investigation has been launched into SNP MP Phil Boswell's use of expenses.
The Independent Parliamentary Standards Association (Ipsa) announced that the compliance officer has opened an investigation into his claims.
Little information was released about the probe into claims relating to the Coatbridge, Chryston and Bellshill MP's office costs.
Ipsa said the investigation was triggered following a complaint by a member of the public.
Compliance officer Peter Davis has faced criticism for settling almost all of his cases without any publicity - despite promising to disclose the outcome of all investigations.
The official notice of the investigation said: "The compliance officer for the Independent Parliamentary Standards Authority has opened an investigation to determine whether Mr Phil Boswell MP has been paid an amount under the MPs' Scheme of Business Costs and Expenses ('the Scheme') that should not have been allowed."
The investigation will be conducted into claims submitted under the heading of "office costs expenditure".
The official notice made clear that no further information would be published until the investigation had concluded.
In January a separate investigation was launched into Mr Boswell's business interests by the Parliamentary Commissioner for Standards.
That probe relates to allegations he contravened parliamentary rules by failing to register his financial interests.
A complaint was reportedly made alleging that Mr Boswell had failed to properly record his directorship of Boswell and Johnston Ltd.
An SNP spokeswoman said: "Phil Boswell will comply fully with the investigation. It would be inappropriate to comment further while the investigation is ongoing."