Extinction Rebellion protesters have descended on Westminster just hours after blocking Oxford Circus with a wooden pyramid structure.
Activists sang and held up their hands, which many had painted red to symbolise blood, outside the gates of Downing Street.
One protester, who appeared to be dressed as Boris Johnson, climbed the scaffolding surrounding Big Ben.
The climate change group are defying a London-wide ban on their protests.
The activist who carried out a “free solo” climb of the scaffolding around the Elizabeth Tower unfurled an Extinction Rebellion banner to “highlight Government inaction on the climate and ecological emergency”.
He was named by the group as tree surgeon Ben Atkinson, 43.
Earlier police used a cherry picker to clear protesters perched on a wooden structure in Oxford Circus.
The gathering at Downing Street is part of a broader demonstration outside government departments in Whitehall.
“We will raise our red hands, taking responsibility for our actions – we all have blood on our hands,” a post on Extinction Rebellion’s website reads.
Alan Partridge actor Steve Coogan joined the procession, which is due to end with a speech in Parliament Square.
It comes despite a ban on two or more people linked to Extinction Rebellion assembling in London, announced by police on Monday.
More than 1,760 arrests have been made in connection with the protests across the capital, according to the Met Police.
The Whitehall procession followed a demonstration at a major junction in Oxford Circus, which police cleared at about 12:00 BST.
Specialist teams brought in a JCB to dismantle the structure that protesters had built in the road.
The Extinction Rebellion London Twitter account said the junction, which was also occupied by the group for several days in April, was targeted because Oxford Street is a centre of fast fashion and is heavily polluted.
It also said the central London street was a “hub of luxury goods for the wealthiest”, citing an Oxfam report from 2015 that claimed the richest 10% of people are responsible for half of all carbon emissions.
The blockade was part of a two-week series of protests, dubbed the Autumn Uprising, which are due to end on Saturday.
Five protesters were charged after rush hour protests at three Tube stations on Thursday.
A spokesman for Extinction Rebellion said: “It’s not about causing meaningless disruption. We have a vital message to bring – the consequences of the climate and ecological crisis are horrific.”
A public order ban has been put in place on Extinction Rebellion activities in London since Monday.
Extinction Rebellion challenged the ban but a High Court judge ruled that a judicial review into the police’s move could not be heard until next week.
The group wanted a hearing before the scheduled end of the protests on 19 October.