© AFPGail Bradbrook smashes a window at the Department of Transport on Tuesday morning.
It came as police ordered the activists to stop their protest immediately or face arrest - as they cleared Trafalgar Square to try and put an end to more than a week's disruption in London.
Climate change protesters were told last night to leave Trafalgar Square, where many have congregated lawfully since Monday last week.
But despite the city-wide ban, the activists continued with their demonstrations on Tuesday morning.
Gail Bradbrook, the group's co-founder, led a protest at the Department for Transport in London where she "lightly" hit the window with a hammer.
© AFPThe Extinction Rebellion co-founder was arrested this morning.
She put a sign up reading "HS2 is our climate emergency" above the revolving doors.
She said: "I do this for the beautiful pear tree at Cubbington Woods, 250 years old they have no rights, I do this in fierce love of the 108 ancient woodlands threatened by HS2, this climate crime of a project.
"I do this in the spirit of what Emmeline Pankhurst called 'the noble art of window smashing'".
She was later brought down by police. A series of dents and a long crack were left on the window.
Other activists glued themselves to the building, while one protester tried to lock herself to the building but was arrested.
At rush hour, they attempted to block off the Marylebone Road, outside Baker Street station.
Extinction Rebellion protesters locked themselves to a caravan parked outside Millbank tower. Police spent more than two hours cutting out the activists using electric saws.
Police said 1,445 people had been arrested during eight days of Extinction Rebellion protests in London.
Extinction Rebellion protesters outside MI5 Headquarters on Millbank.
Police are facing growing criticism over the London-wide ban on Extinction Rebellion protests.
In response Shadow Home Secretary Diane Abbott said the ban was "completely contrary to Britain's long-held traditions of policing by consent, freedom of speech, and the right to protest".
London Mayor Sadiq Khan added: "I believe the right to peaceful and lawful protest must always be upheld."
Human rights lawyer Adam Wagner called it "draconian and extremely heavy-handed", while Allan Hogarth from Amnesty International said it was "unacceptable".
The group's police liaison Paul Stephens said he had "serious doubts" about the legality of the police banning action by activists.
Extinction Rebellion said it has taken the first steps towards a judicial review of Scotland Yard's attempts to restrict their protests.
Four people in a so-called peace tent on Trafalgar Square, who had locked themselves together, were cut out of their locks with machinery last night.
Pam Williams, 71, said: "Everyone on the site, despite being the only area of London that was free of the Section 14, was told at about 8.30pm that they had to leave by 9pm or they would be arrested. I just feel like that's very short notice.
"I feel possibly that they've been approached by people we've upset [on Monday], maybe the finance sector or the banking sector."
Patrick Thelwell, 20, who has been arrested four times, and convicted once with Extinction Rebellion, said the police were getting "desperate".
He said: "They're running out of police cells and resources to keep our message oppressed.
"We're not here against the police, they're just doing their job, they're being really helpful...making sure people's stuff doesn't get lost."
Ellie Chowns, a Green Party MEP, said she was arrested after "standing in solidarity" with protesters in Trafalgar Square.
Hmmm. I guess that was probably an official body, rather than me tearing that hippy vegtard a new one when she tried to hand me a leaflet and 'educate' me the other day in front of The Bank of England.
Despite having all the right PR, Extinction Rebellion are really starting to become a kingsize drag about the place for a lot of people. With any luck they'll be as popular as the clap by Christmas.