BORIS Johnson has dropped a Whitehall investigation into Tory MP Mark Field’s clash with a climate change protester.

Field had been suspended as a Foreign Office minister by Theresa May after he manhandled Greenpeace activist Janet Barker at a high-profile dinner, but retained the party whip.

A Cabinet Office probe into whether he breached the ministerial code has been dropped as Field is no longer a minister, having been fired by Johnson.

A Number 10 source said Johnson believed the incident should have been dealt with by May while she was still in office.

“Mark Field has now left the Government,” the source said.

“The current PM considers this issue was a matter for the previous PM concerning his conduct during his time as a minister under her appointment.”

The Cities of London and Westminster MP was a prominent supporter of Johnson’s leadership rival Jeremy Hunt.

Field clashed with Barker as Greenpeace protesters disrupted the black-tie Mansion House event in the City of London.

At the time of the incident in June, Barker said she had been left “shaken up” after Field grabbed her by the neck and marched her out of the room as Greenpeace staged a peaceful protest, and suggested he take anger management classes.

“I was armed with peer reviewed science – the message that we were giving out. That’s all I was armed with,” she said.

Labour MP Louise Haigh, the shadow policing minister, said: “Never mind not being fit for a job in government, Mark Field isn’t fit to be an MP. It’s not good enough for the prime minister to say that he considers the matter settled.

“Having previously failed to condemn his actions, this is a test of Boris Johnson’s attitude towards women. He should kick him out of the Conservative party immediately.”

City of London police had already dropped their investigation into the incident.

They had been investigating third-party reports of assault against Field, but later decided to take no further action.

Field claimed to have been acting “instinctively”, and said he feared at the time that the protester could have been armed.

In a statement prior to the investigation being dropped, Field said: “I deeply regret this episode and unreservedly apologise to the lady concerned for grabbing her, but in the current climate I felt I needed to act decisively to close down the threat to the safety of those present.”