A Sinn Féin MLA has called on his party's government partners to take action against Ian Paisley and his "rogue activities."
The Westminster Standards Commissioner found that the DUP MP had broken the code of conduct by failing to register a luxury family holiday in the Maldives in 2016 with the parliamentary authorities.
It is the second time the North Antrim MP has been forced to apologise for foreign holidays.
The 2016 trip was investigated by a Standards Commissioner who found that while the politician had not acted in breach of any rules on the declaration of interests nor the rules on paid advocacy, it was a corporate body rather than a personal friend of Mr Paisley who absorbed the cost of the hospitality.
Kathryn Stone said Mr Paisley, his wife and two sons, received a full-board five-night stay at a resort.
Ms Stone said it should have been notified in the Register of Members' Financial Interests.
"The hospitality Mr Paisley and his family received was a registrable benefit, which he should have registered in the Register of Members' Financial Interests within 28 days of the end of his holiday. I therefore found that Mr Paisley acted in breach of paragraph 13 of the 2015 edition of the Code of Conduct for Members," Ms Stone found in her report.
"On the basis of all the evidence available to me, bearing in mind that I had concluded that the true donor had been a corporate body and not a foreign government, I did not find that Mr Paisley had acted in breach of the rules on the declaration of interests nor the rules on paid advocacy."
However, Ms Stone said her investigation had taken too long to complete, adding that much of the delay was the result of Mr Paisley "focusing his attention on rebutting allegations made in the media rather than on answering specifically my questions about his adherence to the rules of the House".
Following a separate inquiry by Ms Stone, Mr Paisley was previously suspended from the House of Commons for 30 days for "serious misconduct" for failing to declare two family holidays to Sri Lanka in 2013.
Ms Stone said Mr Paisley had "acknowledged this new breach of the rules" had "apologised unreservedly for it."
Sinn Féin assembly member Philip McGuigan asked: "How many times will Ian Paisley have to display outright contempt for the public and transparency before the DUP take action against his rogue activities?
"This is the latest in a series of scandals involving Ian Paisley and is another two fingers up to the people of North Antrim by the MP.
"The DUP leadership need to take action against this MP".
The DUP did not respond to a request for a comment.
