He has been stood down from all his National portfolios, with leader Christopher Luxon saying van de Molen's behaviour "is not up to the standards I expect of National MPs".
An independent reviewer found the National MP's conduct "as a whole was aggressive in the sense of being hostile, unprofessional and... with an element that was objectively threatening, but not in the sense of physical violence".
The Privileges Committee accepted van de Molen did not intend to threaten or intimidate Labour MP Shanan Halbert, but the factors in the incident "justify a finding that his conduct was objectively threatening".
Van de Molen contested the claims of being threatening but after the report was released on Thursday, he apologised to the House and accepted the findings. He expected to be censured next week.
"I am horrified at the thought of my conduct being perceived as threatening," he said.
"This is not at all in my nature and I have enjoyed working constructively with MPs across the House. Obviously, in this instance, I have fallen short of my own expectations and the expectations of the House.
"No one should feel threatened in their workplace and it was certainly not my intent to threaten Mr Halbert. Regardless, my conduct was not appropriate and it should not have happened."
Speaking on Thursday afternoon, Halbert said the incident had been "really intimidating".
"I certainly did feel threatened at the time. I was seated and Tim was standing. But I have accepted his apology and I will work with him in the future," he said.
It was alleged that during a Transport and Infrastructure Select Committee meeting in June, van de Molen "threatened and physically intimidated" chairperson Halbert after becoming frustrated by the number of questions allocated to Opposition MPs. Van de Molen contested the claims.
"The Privileges Committee has considered the question of privilege and recommends that Mr van de Molen be censured by the House for threatening a member on account of their conduct as a presiding officer and impeding them in the discharge of their duties as a member," a report released on Thursday says.
The report produced by the Privileges Committee can be found here.
The complaint came from Halbert's Labour colleague Rachel Boyack, who said van de Molen stood over Halbert after the hearing and became "physically and verbally aggressive".
According to the report produced by the Privileges Committee, Boyack said that after being asked by Halbert to move so he could leave the room, the National MP "aggressively asked Mr Halbert to 'stand up'" in a manner that was "suggestive of possible physical violence". It was claimed that van de Molen left the room a short time after "in an aggressive manner".
"Ms Boyack alleged that this incident impeded Mr Halbert’s ability to discharge his duties as chairperson of the select committee, his ability to move unobstructed and unhindered around Parliament, and his ability to participate in proceedings of the House. "
However, according to the report, van de Molen said his recollection of events significantly differed.
"He said that he told Mr Halbert to 'stand up' while still seated in the second Opposition chair (that is, one seat removed from the chairperson’s seat), and that he had intended this to mean that Mr Halbert should stand up for 'the integrity of the committee & fair process'."
The National MP "absolutely rejected" his comment was "in any way a suggestion that a physical altercation was desired". He said he rose to return a water glass and faced Halbert, but denied standing over him or blocking him. He said there was a chair between the two men at the time.
"Mr van de Molen contested - either directly or indirectly - the three claims made by Ms Boyack about Mr Halbert being impeded," the report said.
After the allegation was referred to the Privileges Committee by the Speaker earlier this month, the committee appointed an independent barrister, Wendy Aldred, to carry out a review of the incident and establish the facts.
A summary of her findings found that van de Molen became frustrated with the question allocation and approached Halbert during an exchange. However, he did not "stand over" him as alleged, "being about three-quarters of a metre away from Mr Halbert in the confined space".
With regard to the "stand up" comment, the reviewer found "that he said that to Mr Halbert while he was standing within a short distance of Mr Halbert’s chair, facing him, and that it was a challenge to Mr Halbert to rise to his feet".
"Mr Halbert reasonably took this to be a threat to his safety: objectively viewed there was a threatening element in Mr van de Molen’s conduct.
"Mr van de Molen stood between Mr Halbert and the members’ exit and by not moving when asked to do so on a number of occasions, he effectively prevented Mr Halbert from leaving when he initially wanted to leave. This lasted about 30 seconds, from the second 'move on' (when Mr Halbert expressly stated that he wanted to leave) until Mr van de Molen eventually left."
The reviewer found van de Molen's conduct as a whole "was aggressive in the sense of being hostile, unprofessional and (as stated above) with an element that was objectively threatening, but not in the sense of physical violence".
"Mr van de Molen’s conduct caused discomfort for all three of the Parliamentary staff who were present at the time and each considered the need to ring for security. None of them described a more enduring impact.
"Mr van de Molen’s conduct after the morning Estimates hearing impeded Mr Halbert’s ability to perform his duties as Whip in the House that morning and to attend a debate outside of Parliament later that day. [The reviewer did not find] it materially affected Mr Halbert’s ability to perform his duties as Chair of the Transport and Infrastructure Committee."
The Privileges Committee found van de Molen's conduct "towards Mr Halbert amounted to threatening him, that Mr Halbert was impeded in the discharge of his duties as a member, and that in doing so, Mr van de Molen committed a contempt of the House".
It accepted he did not intend to threaten or intimidate Halbert, but the factors in the incident "justify a finding that his conduct was objectively threatening".
"Acting in a threatening manner toward a member of Parliament on account of their conduct in Parliament, and particularly for their conduct as a presiding officer, is a serious matter.
"We therefore recommend that Mr van de Molen be censured by the House for threatening a member on account of their conduct as a presiding officer and impeding them in the discharge of their duties as a member."
In a statement after the report was released, Luxon confirmed van de Molen had been stood down from all his portfolios, including building and construction, defence and ACC.
"I have made clear, both to National MPs and to the New Zealand public, that I expect high standards of behaviour and will hold my team accountable for their actions. I mean it," Luxon said.
"My role is to lead an alternate government and I expect all National MPs and candidates to be focussed on promoting National’s policies to rebuild the economy, bring down inflation, restore law and order and fix health and education so we can get New Zealand back on track."
Luxon said van de Molen had had a difficult year personally - he broke both of his arms last year and lost his younger sister earlier this year - but that didn't excuse the behaviour.
"Tim accepts all the findings and has publicly apologised. He has also committed to seeking coaching support to ensure this doesn’t happen again."
He said people made mistakes and there was a pathway back for van de Molen as long as he can "demonstrate to me, the wider National caucus, and himself, that he has learnt from this incident and grown as a result".
National MP Andrew Bayly takes the building and construction role, Gerry Brownlee gets defence and veterans, and Simon Watts gets ACC.
Van de Molen was the fourth MP this year alone to be sent to the Privileges Committee after Jan Tinetti, Simon Court and Michael Wood.
Tinetti, was found not guilty of contempt in June over her delay to correct an inaccurate statement made in Parliament, but was forced to apologise.
Court was found to have committed a "clear breach" of confidentiality rules by revealing committee information in a press release.
Wood was referred last month over his shares saga. On Wednesday, he apologised over his failure to properly declare his shareholdings.