Mark Field has been suspended as a government minister after violently grabbing a Greenpeace protester by the neck.

The Foreign Office minister was widely criticised after a video emerged of the incident at a City of London dinner on Thursday night.

It showed him jumping out of his seat to block the activist, grabbing her around the back of her neck, pushing her up against a column and then marching her out of the room.

The incident took place at a black-tie Mansion House dinner, where Philip Hammond, the chancellor, was giving a speech.

Amid a growing backlash over his actions, Mr Field referred himself to the Cabinet Office and is also being investigated by police.

Downing Street said he would be suspended as a minister “while investigations take place”.

A spokesperson said: “The prime minister has seen the footage and found it very concerning. The police have said they are looking into reports of this matter and Mark Field has reported himself to the Cabinet Office and Conservative Party.

“He will be suspended as a minister while investigations take place.”

The spokesperson said the Cabinet Office’s propriety and ethics team would look into whether there had been a breach of the ministerial code.

They said: “We would like it to happen swiftly. I can’t put a time on it, but as quickly as possible.”

It is understood that Theresa May spoke with Julian Smith, the government chief whip, about the incident after flying back to London from the European Council summit in Brussels on Friday morning. Mr Smith passed on her decision to suspend Mr Field to the minister. The prime minister has not spoken to Mr Field herself.

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The Cities of London and Westminster MP had earlier apologised “unreservedly” to the activist.

He said: “In the confusion, many guests understandably felt threatened and when one protester rushed past me towards the top table I instinctively reacted.

“There was no security present and I was for a split-second genuinely worried she might have been armed.

“As a result, I grasped the intruder firmly in order to remove her from the room as swiftly as possible.”

Mr Field is supporting Jeremy Hunt, his boss at the Foreign Office, in the Tory leadership contest.

Asked about the row, Mr Hunt said: “Mark has issued a full and unreserved apology. He recognises that what happened was an overaction. What we need now, in his interests but also in the interests of the lady involved, is a proper independent inquiry by the Cabinet Office. That’s what is going to happen.”

The minister was strongly condemned by MPs from opposition parties.

Dawn Butler, the shadow women and equalities minister, said the incident “appears to be assault” and called for Mr Field to be “immediately suspended or sacked due to violence against women”.

Who is suspended Tory MP Mark Field?

Sadiq Khan, the mayor of London, said: “It is truly shocking to see this kind of behaviour from an MP. Violence against women is endemic in our society and this behaviour is unacceptable. He should consider his position.”

But some Conservative MPs defended their colleague.

Sir Peter Bottomley said: “I think there’s no reason to criticise Mark Field ... Of course, it wasn’t an assault, it was a reversal of direction.”

Johnny Mercer added: “Try being in our shoes in the current environment. He panicked, he’s not trained in restraint and arrest, and if you think this is ‘serious violence’, you may need to recalibrate your sensitivities. Calm down, move on, and be thankful this wasn’t worse.”

The protest took place as Mr Hammond was beginning his speech at the dinner and lasted for several minutes before the chancellor was able to finish his remarks.

Greenpeace said around 40 of its activists had interrupted the event.

It tweeted on Friday morning to say the activist involved in the incident with Mr Field “had a good sleep and is doing fine”.

It said: “We’re looking after her. Thanks so much for your love and concern everyone. We’re sharing positive messages with her.”

The protester, who was later named as Janet Barker, said she would not be pressing charges against Mr Field – but suggested the MP should go on an anger management course.

She told the BBC: “He certainly manhandled me in a way which was very disagreeable to myself and to most people.