DUP MP Ian Paisley has apologised in the House of Commons and admitted “deep personal embarrassment” after failing to declare two luxury holidays paid for by the Sri Lankan government.
Choking with emotion at times, Mr Paisley said he had made a “genuine mistake”.
The North Antrim MP is facing calls to stand down from Westminster over the controversy.
He has made it clear privately that he has no intention of doing so.
However, the decision could be taken out of his hands.
A parliamentary watchdog has recommended that he be suspended from the Commons for 30 days, and the controversy also has the potential to trigger a by-election.
The MP faces a 30-day suspension after he failed to declare the details of two family holidays in 2013 paid for by the Sri Lankan government.
Any suspension would deprive Prime Minister Theresa May of a vote on key Brexit issues.
The claims first appeared in the Daily Telegraph in September 2017.
By Mark Simpson, BBC News NI
So often Ian Paisley is accused of being bullish, but in the Commons today he was distinctly sheepish.
His voice cracked with emotion at times during a personal statement which may have felt like the longest four minutes of his political career.
Cynics will say he is already in election-mode, looking for the sympathy vote with a by-election now likely.
Others will say that in the world of politics, where sorry is the hardest word, this was a genuine moment of Paisley repentance rather than no surrender.
The recommendation to suspend Mr Paisley will now go before the House of Commons next Tuesday for approval, in the form of a motion.
Tuesday marks the last day of business in the Commons before the summer parliamentary recess begins.
If the motion is passed, Mr Paisley’s suspension from the Commons will begin on 4 September and will last for 30 sitting days – meaning he would be unable to return to his duties until mid-November.
However, there is an added complication that Mr Paisley faces if the 30-day ban is accepted.
It could trigger a Recall Petition, by which an MP can lose their seat if 10% of the eligible electorate in their constituency signs a petition.
But the MP would be free to stand again in the subsequent by-election and it is understood Mr Paisley has indicated he would do so.
In the likely event that Mr Paisley’s suspension comes into effect, it will cause difficulties for the government in the autumn on crucial Brexit votes.
The government relies on the votes of the 10 DUP MPs to get legislation through the house. Numbers are already on a knife-edge and this will leave Mrs May with one less MP to rely on.
In his statement to MPs in the Commons, Mr Paisley said he accepted his “total failure”.
He also accepted the investigation’s findings but was disappointed he was not able to persuade members of the standards committee that there had been no ulterior motive to his actions.
“I accept the report, but I do so regret its sanctions,” he said.
Mr Paisley said he took his duties as an MP seriously and that he felt remorse about the nature of what had occurred.
He was seated among several of his DUP Westminster colleagues, including Sammy Wilson and Jim Shannon.
He said he made the “profoundest of apologies” to his North Antrim constituents, whom he has represented since 2010.
“We all know that in public life, if you make mistakes they are amplified and rightly so – that’s the nature of the job,” he said.
“I believe in politics and politicians that can apologise, can mean it and move on – that’s what real life is all about.”