Seven people have been arrested after attacks on four political party headquarters, in which paint was reportedly thrown and windows broken.
The Metropolitan Police sent officers to buildings used by the Conservatives, Labour, the Lib Dems and the Green Party in London.
Pictures posted on Twitter by the Beyond Politics Party show pink paint daubed on masonry and windows.
Five people were arrested on suspicion of causing criminal damage.
Two more were held on suspicion of burglary.
The incidents took place early on Thursday morning in Matthew Parker Street, Victoria Street, St Georges Street and Clements Road.
Beyond Politics – which campaigns for “citizen-led decision making” and was launched in June – accused all the parties targeted of being “part of this corrupt and failing system” and failing to protect the environment.
One member said: “We are here today because neither the government nor any of the political parties are effectively standing up for the planet.”
Beyond Politics’s Twitter feed shows a man dressed as a priest and a woman in a pink T-shirt standing outside Conservative Party HQ in Matthew Parker Street, holding a banner saying: “Treason, Treason, Treason.”
They are also pictured sitting on the steps of Liberal Democrat HQ in George Street, with pink graffiti on the walls and windows behind them.
Labour, whose Victoria Street building had paint spread across much of its front, declined to comment on what it called a “police matter”.
A Liberal Democrat spokesperson said: “Failure to tackle the climate crisis is doing irreversible damage.
“That is why the Liberal Democrats are demanding the prime minister shows leadership by taking urgent action to implement a green recovery and reduce carbon emissions, protecting the planet for future generations.”
A Green Party spokesperson said: “The Green Party has been at the forefront of climate action for many years and will continue to drive forward a more democratic approach to politics which challenges climate and social injustice.
“This is a police matter and so we are unable to comment any further.”
The Conservative Party has also been asked for a response.
The Metropolitan Police said inquiries were ongoing.