SNP MP John Nicolson will face the Privileges Committee after MPs voted to refer him over a letter leak row.
It comes after Speaker Sir Lindsay Hoyle said Nicolson gave a "partial and biased account" of a letter sent to him on Twitter, and MPs held a debate in the House of Commons on his conduct on Tuesday.
Labour told the Commons that they would be backing the motion, brought by Tory MP and former Brexit minister David Davis. The final vote stood at 371 for yes, and 16 for no.
Nicolson was accused of breaching the confidentiality of the Speaker by posting part of his letter relating to a decision on referring Conservative former culture secretary Nadine Dorries to the Privileges Committee.
However, Nicolson told the Chamber he did not reproduce the letter but only summarised its contents and Hoyle's decision not to send Dorries to the committee, adding he was not aware that the correspondence was confidential as it was not marked private.
Hoyle reportedly suffered a social media "pile on", making the issue the first contempt case heard in Westminster caused by Twitter.
Nicolson told MPs: "I’m very sorry that a pile on has ensued, I believe in vigorous but fair debate.
"I have no time for abusive behaviour. I don’t engage in it and I deplore it.
"I’m advised that I’ve breached a parliamentary rule by referring to the speaker’s letter, as I’ve explained I did not knowingly do so.
"I would never reveal a confidence.
"I did not believe the Speaker’s decision on a parliamentary matter was a secret."
Nicolson later added: "I’m slightly torn, I am deeply sorry that the Speaker is upset.
"I don’t conduct politics in a way that ever aims to be offensive, and I’m truly sorry that the Speaker is upset and that I upset the Speaker.
"But it would be disingenuous of me to say that I knowingly revealed this, I could not have been more open than going on camera and discussing this, I wasn’t trying to hide it.
"I suspect that most people will find it curious that the member who misled the select committee was subject to no consequences, but the member who revealed that…"
The Deputy Speaker told Nicolson he "absolutely needs to withdraw the remark", which he did.
However, he added: "These debates had been confined to people sometimes, or accused of committing, some of the more egregious offences.
"I’ve yet to meet a member that thinks this falls into this category."
Earlier, SNP MP Pete Wishart accused the Tories of "institutional bullying" during the debate on his colleague's conduct.
Nicolson, SNP MP for Ochil and South Perthshire, was forced to give a statement to the House of Commons after Speaker Sir Lindsay Hoyle allowed a debate on his conduct to go ahead.
Nicolson was called to apologise by Hoyle last week, for posting part of his letter relating to a decision on referring former culture secretary Nadine Dorries to the Privileges Committee.
Wishart, intervening in the debate, said that despite his 20 years as a Westminster parliamentarian he was not aware that sharing correspondence with the Speaker was privileged.
He said: "How on earth was my honorable gentleman meant to know?
"All of this just seems at best retribution, at worst institutional bullying because that’s what it’s starting to feel like right now."
Penny Mordaunt, leader of the House, said she didn't buy Nicolson's argument that he was not aware of the right course of action regarding the correspondence and said she had hoped he would have made an apology.
She told MPs: "I think there’s a consensus across the House about what the right course of action is now, but I think if the honourable gentleman had taken the opportunity that could have potentially been brought to an end here today."
Nicolson intervened to point out he had apologised on multiple occasions, telling MPs: "I think there’s a misunderstanding there.
"I did quite clearly say I was apologising to the Speaker, I was unaware of this convention. I wished to cause him no hurt and apologised. I’m repeating that now."
Mordaunt, Tory MP for Portsmouth North, replied: "The way the honourable gentleman has phrased this and not appreciating the wrong, not appreciating the damage that has been done in these circumstances."
Thangam Debbonaire, Labour's shadow leader of the House, said that upholding conventions is "essential to the smooth running of this House and to the foundation of political order in this country".
She added that her party would be supporting the motion as Erskine May, the handbook on parliamentary procedure, was clear on the convention surrounding correspondence with the Speaker is confidential "in both directions".
She added: "I therefore believe that the Honourable Member for Ochil and South Perthshire's conduct does therefore warrant an investigation by the Committee of Privileges as requested.
"So I will be supporting this motion today and I urge others to do so."
