Extinction Rebellion have poured a pool of fake oil over the steps of the Labour Party’s London headquarters and let off smoke grenades.
Two activists climbed on to the portico and set off the canisters, while another chained himself to a handrail, calling on Labour to cancel any oil licences granted by the Conservatives before the next election if the party comes to power.
Other supporters held up banners saying “Cut the ties to fossil fuels”.
The action at the building in Blackfriars Road, Southwark, south-east London, on Monday followed an XR protest in Parliament Square on Saturday involving an effigy of Labour leader Sir Keir Starmer dressed as Margaret Thatcher.
A Metropolitan Police spokesman said: “At around 9am on Monday, September 18, police were called to reports of a small group of people reported to be spraying paint on a building in Blackfriars Road, Westminster.
“Local officers arrived on scene while the demonstration was in progress.
“One person had locked themselves onto a pillar on the building and two people had scaled the canopy outside.
“Specially-trained protest removal teams made sure protesters were removed from the building quickly and safely.
“Two men have been arrested on suspicion of criminal damage and remain in police custody at this time.”