Boris Johnson has been forced to apologise to MPs for failing to declare more than £52,000 in income after the Commons standards watchdog suggested he showed an "over-casual attitude" to the rules.
The former foreign secretary offered a "full and unreserved" apology in a 35-second statement in the House of Commons.
The Commons Committee on Standards said Mr Johnson broke House rules by failing to register payments within the required timetable on nine occasions.
MPs have to register any changes to their financial interests each month, but the former Cabinet minister's registrations were late on four separate occasions, involving nine payments, the parliamentary sleaze watchdog found.
Kathryn Stone, parliamentary commissioner for Standards, said the number of late registrations suggested a "lack of attention to the House's requirements, rather than inadvertent error".
But the Committee said there were no grounds for supposing Mr Johnson "intended to deceive the House or the general public about the level of his remuneration", though it criticised his "over-casual attitude" to the rules.
The Committee concluded: "We recommend that Mr Johnson should make an apology to the House, on a point of order, for this breach of the rules.
"We recommend that in that apology he should address the specific comments we make in this report, and that he should undertake to ensure that his future registrations of remuneration are made in a timely way.
"We further recommend that the relevant payments be italicised in the register to indicate that they are late entries."
The nine late registrations had a total value of £52,722.80, and were largely royalties or for the sale of rights on books already written, Ms Stone said.
The Committee noted that aggravating factors in calling for Mr Johnson to apologise included the size of the sums involved, the number of breaches and that he had been an MP over four Parliaments, and had been a senior minister, saying he "could be expected to set an example within the House".
And it said Mr Johnson responded "promptly and helpfully" when the issue was raised to him, apologised to the commissioner and put in place "effective measures to ensure that no further breach occurs".
In his brief personal address to the Commons, Mr Johnson said: "The Committee on Standards has today published a report on nine payments, mainly unexpected foreign royalties, which I am very sorry to say were recorded late on the register of Members' interests.
"I fully accept that the delay was a breach of the House's rules and, though I'm grateful to the committee for recognising that there was no intention to mislead the House and that I had been completely transparent, I therefore offer the House a full and unreserved apology."