MPs have voted to suspend DUP MP Ian Paisley for 30 sitting days.
It follows his failure to declare two family holidays paid for by the Sri Lankan government. He will be absent from Parliament for some key Brexit votes.
He has also been suspended by the DUP "pending further investigation into his conduct".
Speaker of the House John Bercow called it "a regrettable state of affairs".
Mr Bercow will now formally inform the chief electoral officer of the decision and she has ten working days to set up a petition which, if signed by 10% of North Antrim constituents, will lead to a by-election and Mr Paisley having to stand down.
Sir Kevin Barron, chair of the Standards Committee, said they had concluded Mr Paisley was guilty of "serious misconduct and his actions were of a nature to bring the House of Commons into disrepute".
He also said the inquiry into Mr Paisley could have been concluded earlier: "The process could have been considerably shorter if Mr Paisley had been more cooperative initially."
Sir Kevin said Mr Paisley did show a "greater sense of urgency" in the later stages of the investigation.
Key points from the Standards Committee's findings
- Mr Paisley went on three luxury holidays to Sri Lanka at the expense of the Sri Lankan government in 2013.
- The committee found the cost "much higher" than the £50,000 Mr Paisley estimated.
- In 2014, Mr Paisley wrote to the prime minister to lobby against supporting a UN resolution on Sri Lanka over alleged human rights abuses.
- By failing to declare his trip, Mr Paisley "breached the rule against paid advocacy, the committee said.
- The committee acknowledged that there was "inconsistent guidance" in relation to registering such trips, but it did not "exonerate Mr Paisley from breaching the advocacy rule".
This is one of the longest bans ever to be handed down at Westminster.
'He's a Paisley'
Analysis by political correspondent Gareth Gordon
Suspended by fellow MPs, and now the party his late father once ruled without dissent, these are difficult days for Ian Paisley Jnr.
It's not the first time he's fallen foul of the DUP leadership but this is by far the most serious.
He's made it clear he intends to fight any subsequent by-election. But what will the DUP leadership do?
Some would undoubtedly like to say farewell to him for good.
But... first of all he's a Paisley.
Secondly, he's popular with the unionists of North Antrim who may not forgive the party if it cast him permanently aside.
The DUP had to do something and they've done it.
But the smart money says that after a period of suspension, Ian Paisley will still be the DUP candidate should North Antrim go to the polls before the end of the year.
Mr Paisley has insisted he will fight any by-election to save his Westminster seat if he is forced to stand down.
Mr Paisley's party plays a pivotal role in supporting Theresa May's minority government.
In June 2017, an agreement was reached that the 10 DUP MPs would back the Tories in key Commons votes.
Writing in the Ballymena Guardian on Tuesday, the North Antrim MP said he was prepared for whatever punishment came his way.
He called those pushing for such an election "opportunists", but made it clear that he would not run away from any challenge.
The Officers of the Democratic Unionist Party have considered the report of the House of Commons Committee on Standards on Ian Paisley MP.
The Party takes this report and the matters contained within it very seriously.
The Party Officers have decided to suspend Mr Ian Paisley MP from membership of the Party pending further investigation into his conduct.
The Party does not intend to make any further comment on these matters during the course of the above outlined process.
Mr Paisley failed to declare two luxury family holidays in 2013 paid for by the Sri Lankan government.
He later lobbied the then prime minister on the country's behalf.
Speaking on BBC Radio Ulster's Stephen Nolan Show on Wednesday, the political editor of the News Letter, Sam McBride, described the scale of the punishment as "new territory" for the House of Commons.
"This is not some minor breach of parliamentary protocol - this is something that parliament frowns upon in such a way that under this new law, they now give voters in his constituency the chance to remove him from his seat so it's very different to what has gone before."
Although the DUP said party officers took the decision to suspend Mr Paisley, Mr McBride said he believed the leader of the party, Arlene Foster, would have approved it.
"The leader is ultimately the person who carries the can for this," he said.
"If you're the leader of a party, you call the shots. It's pretty difficult to believe Arlene Foster was not in support of this."