Justice secretary Jack Straw and former minister Peter Hain have been criticised for failing to register donations.
Straw was guilty of failing to register a donation made to him in 2004, the Commons standards and pribvileges committee ruled on Thursday.
The MPs said this was "a clear, albeit inadvertent, breach of the rules of the House".
Despite having been reminded on three occasions of the need to register the donation in question, the justice secretary failed to do so.
"Mr Straw has called this a chapter of accidents," said the MPs. "Accidents generally happen as a result of negligence, and Mr Straw has clearly been negligent in this case."
The committee said it was "surprised and disappointed that, of all members, Mr Straw should have broken the rules".
The MPs said the former leader of the Commons may have overlooked his responsibiliities due to pressure of work, but added that "the nature of his job should also have been a constant reminder to him of the need to observe the code".
Straw "apologised unreservedly" for the error, leading the MPs to recommend no further action.
Hain, the former work and pensions secretary who was forced to resign from the cabinet because of the row over his expenses, was told he should now issue a personal apology on the floor of the Commons.
The Labour MP had registered 10 donations he received towards his deputy leadership campaign within the four-week deadline.
But he registered two further donations late, in November and December 2007, with a combined value of £10,000.
And he then registered 17 further donations late in January 2008, totalling more than £103,000.
The standards committee said that the pressures of work on frontbenchers may be a factor, but added that "we cannot accept – and we are sure that none of them would suggest – that this excuses them from their obligations under the rules of the House".
The committee concluded that Hain's "failure to register donations on this scale is both serious and substantial".
"We are bound to take this into account, notwithstanding the facts that Mr Hain has apologised unreservedly, and that he acted with commendable speed to rectify his omissions once he discovered them, without waiting for others to invite him to do so," said the report.
"Because of the seriousness and scale of this breach and noting the considerable, justified public concern that it has created, we would ordinarily have been minded to propose a heavier penalty.
"However, we accept that there was no intention to deceive and Mr Hain has already paid a high price for his omissions.
"We therefore recommend that Mr Hain apologise by means of a personal statement on the floor of the House."
23 January 2009