Her office says Friday that May saw the footage and found it "concerning." City of London Police, the Cabinet Office and the Conservative Party are all investigating the Thursday night incident. Video of the incident shows the protester walking behind the seated guests and approaching the head table when Field stops her, pushes her into a pillar and places his hand firmly on her he leads her away.
The protester was from Greenpeace, which did not immediately respond to requests for comment from The Associated Press. The demonstration comes at a time when climate change activists have disrupted life and travel in London, sometimes for days.
Britain's Conservative Party says one of its lawmakers will face an investigation after he ejected a climate protester seeking to interrupt a speech by the nation's Treasury chief at a gala dinner.
Party chair Brandon Lewis says that lawmaker Mark Field referred himself to an investigation by the Cabinet Office after he was filmed grabbing the woman at the Mansion House event on Thursday.
Lewis told ITV it was "very hard to defend" the footage, but says the investigation will look into the "full details of what happened."
Fellow Conservative Peter Bottomley defended Field, saying he "did what any sensible person would have done" in ejecting the protester.
Bottomley told the BBC the demonstrator could have been "carrying a collapsible truncheon."
Treasury chief Philip Hammond continued his speech and defended the government record on climate change.