MPs who have been arrested on suspicion of a serious offence face being barred from parliament under new plans that were approved in a vote this evening.

It comes despite the government putting forward a motion that recommended MPs only face a ban if they are charged with a violent or sexual offence – a higher bar.

MPs voted to reverse moves to water down the measures on “risk-based exclusions” to ensure members can be excluded from the parliamentary estate at the point of arrest for serious sexual or violent offences.

That was the original recommendation put forward by the House of Commons Commission – but it was later revised by the government to raise the threshold for a potential ban to the point of charge.

In a surprise move, MPs tonight voted 170 to 169, a majority of one, in favour of amendment by Lib Dem MP Wendy Chamberlain and Labour MP Jess Phillips to reinstate the original intention of the policy.

The division list showed eight Conservative MPs voted in favour of the opposition amendment, including safeguarding minister Laura Farris, former prime minister Theresa May and backbench MP Theresa Villiers.

Ms Villiers received a suspension from the Commons for one day in 2021 after she and several other Conservative MPs breached the code of conduct by trying to influence a judge in the trial of former MP Charlie Elphicke, who was convicted in 2020 of sexually assaulting two women and jailed for two years.

Tonight’s vote means those who have been arrested on suspicion of a violent or sexual offence will banned from parliament, pending the approval of an independent panel.

Mike Clancy, the general secretary of the Prospect trade union, said the result was an “important and overdue victory for common-sense and those working on the parliamentary estate” while FDA general secretary Dave Penman added: “Parliament is a workplace for thousands and these new formal procedures give staff the safe working environment they deserve and would expect in any other workplace.”

Ms Phillips, who advocated for the case for exclusion at the point of arrest, wrote on X: “Shit! We won the vote by one.”

In the debate preceding the vote, she told the Commons: “Today, just on this one day, I have spoken to two women who were raped by members of this parliament; that’s a fairly standard day for me.

“Exclusion at the point of charge sends a clear message to victims that not only will we not investigate unless a victim goes to the police but we won’t act unless they’re charged, which happens in less than 1% of cases. ‘So what’s the point?’ was essentially what this victim said to me.

“I’m going to stand here and speak up for them because every single one of them wishes for this to be on arrest.”

The exclusion policy was put forward following a number of incidents involving MPs in recent years. Currently, party whips decide if and when an MP accused of an offence should be prevented from attending the parliamentary estate.

The House of Commons Commission originally recommended that a risk assessment should take place on whether an MP should be prevented from attending the parliamentary estate if they were arrested on suspicion of committing a violent or sexual offence.

But the plans were later scaled back following objections from some Tory MPs and fears of “vexatious” claims.

Commons leader Penny Mordaunt, the proponent of the plans to raise the exclusion threshold to charge rather than arrest, said the number of MPs and Lords that had been victim of “vexatious” harassment claims was “surprisingly large”.

“Many members raised the comparison about the profession that we’re in and other professions, particularly the police force, and of course the police themselves may be also subject, not infrequently, to vexatious claims made against them for all kinds of reasons.

“But I would say the volume of members of both Houses that have come to see me during this process, who have been victim of vexatious claims, was surprisingly large.”

Ms Mordaunt also clarified that the risk-based exclusion practices would apply to the Speaker and deputy-speakers, stating “if they were panel members, they would clearly recuse themselves as they would in other scenarios”.

Former minister Sir Jacob Rees-Mogg used the debate to describe the exclusion plans as an “extraordinary power grab by standing orders to undermine a fundamental of our constitution” while Sir Michael Ellis, a former attorney general, also said there were constitutional and legal implications to excluding MPs on arrest.

“There is a key principle here, there’s a golden thread that runs through our system that a person must not suffer imposition before guilt has been proven,” he said.

“And it is offensive against the laws of natural justice, and in fact contrary to human rights to do so.”