A Tory MP has resigned from parliament's sleaze watchdog after failing to declare hundreds of thousands of pounds of outside income on time.
Backbencher Geoffrey Cox QC has apologised and referred himself to the standards commissioner after breaking time limits on reporting earnings from hundreds of hours of legal work.
The Torridge and West Devon MP is known as one of parliament's highest earners, and has argued that continuing to practise law alongside his parliamentary duties means he has "practical experience of a world outside politics".
According to the latest register of members' financial interests, Mr Cox received £325,000 on June 15 and 16 this year for 500 hours of work carried out between June 2014 and March 2015.
Under Commons rules external income needs to be registered within 28 days, but the sum was not declared to the authorities until September 30.
A number of other payments also appear to have been registered late.
Mr Cox said he had always intended to declare the income but recognised he had breached rules.
"I have referred myself to the Parliamentary Commissioner for Standards following the late registration of payments received for my continued practice at the Bar," he said.
"While there was no intention not to declare these sums, I recognise that the failure to do so in a timely manner is a clear breach of the required 28-day notification period.
"I wish to apologise unreservedly to my constituents and to the House for this error and for my failure to give these matters their due priority."
A spokesman for Mr Cox said although no conflict of interest had been identified, the MP felt it was "no longer appropriate" for him to remain a member of the cross-party Standards Committee.
Parliamentary standards commissioner Kathryn Hudson's office confirmed that she has launched a formal investigation into Mr Cox over registration of financial interests.