The Reform UK MP Lee Anderson has been ordered to apologise by parliament’s watchdog for bullying and harassment, after it found he told a security guard to “fuck off, everyone opens the door to me”.

The MP for Ashfield, who was the deputy chair of the Conservatives at the time, was found to have twice sworn at the security officer and acted in a way that “constituted bullying, and also harassment” in breach of parliament’s behaviour policy.

The security officer told an investigation that Anderson had instructed him to open a door. He said when he asked to see the MP’s parliamentary pass, Anderson said: “Fuck off, everyone opens the door to me, you are the only one.”

The officer said he explained he would need to check the MP’s pass, and that Anderson replied: “Fuck you, I have a train to catch,” before walking out of the search post.

A report by the independent expert panel, which makes determinations on parliament’s bullying and harassment code, found that Anderson should apologise to the complainant and to the House of Commons.

It was originally examined by an investigator from the Independent Complaints and Grievance Scheme, with the finding upheld by parliament’s standards commissioner.

A subgroup of the independent expert panel found that the security guard was left upset and intimidated, and the incident led to him moving to a different job in parliament. It highlighted as an aggravating factor the power imbalance between Anderson as an MP and the complainant as a security officer.

It also took into account Anderson’s evidence of “challenging personal circumstances which affected him on the day of this event” and found that his behaviour was not planned or premeditated.

During the investigation, Anderson accepted that he was “upset, impatient and angry” but not “aggressive”, and denied swearing at the complainant.

He tried to appeal against the finding of commissioner, saying: “The allegations made against me are untrue and there is absolutely no evidence at all to prove or disprove what I said during the brief exchange I had with the security guard. There is simply some CCTV footage without any sound and to be honest I found the interview I had to be very unfair at the time – it felt to me that the investigating officer had already made his mind up.”

Anderson was denied an appeal as he had not provided grounds that the process was flawed or any credible fresh evidence.

After the appeal was denied, he gave oral evidence to a hearing of the sub-panel last month. The report after the hearing said Anderson “has now accepted the facts of the incident without equivocation”.

“He also accepts that he used the intemperate language alleged, and that the complainant must have been upset,” the report said.

Anderson resigned as Tory deputy chair in January to vote against Rishi Sunak’s Rwanda bill. He then lost the Conservative whip in February after refusing to apologise for saying Islamists had “got control of” the Labour London mayor, Sadiq Khan, who had “given our capital city away to his mates”.

He defected to Reform UK in March and subsequently held his Ashfield seat at the July general election.