A Tory MP has made a "sincere and heartfelt" apology to the House of Commons after failing to declare more than £400,000 of outside income on time.
The cross-party Standards Committee found Geoffrey Cox QC had committed a "serious" breach of rules - although it accepted he had not "intended to hide" earnings for hundreds of hours of legal work.
The Torridge and West Devon MP blamed the ill-health retirement of the head clerk at his barrister chambers for the "oversight".
In the past the clerk had "drawn the receipt of payments to my attention", he told the parliamentary standards commissioner.
Between January and August last year he received 11 payments totalling more than £400,000, but did not declare them until the end of September - way over the 28-day deadline.
Mr Cox said part of the reason he had not noticed the problem earlier was because he spent the summer recess launching "an entirely new international law chambers based in Mauritius and Dubai".
He referred himself for investigation and resigned as a member of the Standards Committee on becoming aware of the breaches.
In its report the committee said: "We accept that Mr Cox had no intention to hide these payments and that he has not breached the requirements of the House for declaration of relevant interests.
"Nevertheless, as the commissioner notes, the number of payments and the sums involved in the late registration are significant and Mr Cox was in a position which should have ensured that he was more familiar with the rules and the relevant principles of public life in this area than other Members might be.
"Mr Cox has already apologised to the Registrar and the Commissioner. We recommend that Mr Cox make an apology to the House for his failure to register payments in a timely fashion."
In his evidence to the commissioner, Mr Cox stressed he had always been open about the scale of his outside earnings - which amounted to some £800,000 in 2014.
But he said: "I failed to give this matter the due thought and priority it required and, for that reason, it is difficult to isolate the exact point at which I became aware that my entry was incomplete.
"When the House rose for the summer, I was conscious, generally, of the matter as one I needed to get down to checking but my intense schedule at the time, which included the final planning and launch during recess of an entirely new international law chambers based in Mauritius and Dubai, meant that it was not until reviewing my records between September 20 and September 28 that, to my dismay, I became fully aware of the scale of my oversight.
"I fully acknowledge that this was not acceptable and I have taken all necessary steps to ensure that it does not happen again."
Mr Cox said his head clerk was with him for 29 years, and "had full access to, and oversight of, the details of my professional practice including my personal bank accounts".
"He acted in many respects as my personal confidential secretary, including managing many of my financial affairs, even meeting the bank manager on my behalf, and he would draw the receipt of payments to my attention on an ad hoc basis, acting as my prompt for registration. He was also in direct and frequent contact with my parliamentary office as manager of my diary," the MP added.
Delivering his apology to the House in the wake of the report, Mr Cox said: "In 2009 the House resolved that honourable members should register all outside earnings within 28 days of their receipt whether connected with their parliamentary duties or not.
"For a prolonged period last year I very much regret that I failed to comply with that rule in respect of my professional earnings as a barrister.
"The House has a right to expect of its members, and particularly those on the Standards Committee as I was, that they will uphold its rules to the fullest extent.
"For this reason I have stepped down from the Standards Committee and I hope that the House will accept my sincere and full hearted apology for my failure to observe this important rule."