An Extinction Rebellion protester has scaled the scaffolding surrounding Big Ben and draped two banners from the structure.
Footage of the stunt circulated on social media showed the climber, who appeared to be dressed as Boris Johnson complete with a blond wig, shirt, tie and jacket.
A spokesperson for the group said the climber was 42-year-old tree surgeon Ben Atkinson.
He said Atkinson was climbing the tower to “highlight Government inaction on the climate and ecological emergency”.
The protester, who was also wearing green leggings, draped two signs carrying the group’s slogans.
One featured the Extinction Rebellion logo on a rainbow background and the words “No pride on a dead planet” and the other said “Citizens Assembly”.
It is the latest in a string of stunts staged by Extinction Rebellion on the penultimate day of their autumn uprising – despite being banned from protesting in the capital since Monday by the Met Police.
Yesterday, the group was forced to apologise after holding up Jubilee Line trains by climbing on them.
One protester was filmed lashing out at an angry commuter who had pulled him off the roof of a train.