Climate activists posing as tourists have superglued themselves around the Speaker’s chair in the House of Commons chamber.
Extinction Rebellion (XR) said around 50 people were involved in the “non-violent” action at the Palace of Westminster.
They said three people booked on an official tour of the building glued themselves in a chain around the Speaker’s chair before they read out a speech in support of a citizens’ assembly to act on climate matters.
The campaign group posted a photo on Twitter showing the three members hand-in-hand in front of the seat, with two other members holding up signs.
One protester climbed up scaffolding inside the parliamentary estate near Westminster Hall and held a banner that read: “Let the people decide, citizens’ assembly now.”
Two of its members also used bike locks to chain themselves to the railings to the New Palace Yard entrance gates.
Police responded in a bid to deal with the protesters inside and outside the building.
An XR activist, who would only give his name as Al from Northamptonshire, said demonstrators had smuggled banners into the Commons chamber in a “bag within a bag”.
He said: “The action today was to form a circle around the Speaker’s chair. People glued themselves around the Speaker’s chair, they didn’t damage the Speaker’s chair in any way, and they glued themselves to each other.”
XR protester Joe Short, from Bristol, said: “I have locked myself to the railings outside the Houses of Parliament.
“It is part of a bigger protest which is about climate inaction but it is also about a citizens’ assembly which is an alternative form of democracy which could be much more effective at dealing with problems like climate change.”
Asked if he was uncomfortable chained to the railings and surrounded by police officers, Mr Short said: “At the end of the day, in the scheme of things, it is not such an uncomfortable position.”
XR demonstrator Lisa from Newbury joined fellow protesters outside the gates of Parliament.
She said: “We are here today because we are addressing the seat of power here in Parliament, because it is not working. It is broken.
“We have got a horrendous climate crisis, a huge, obscene, terrible cost-of-living crisis and it is not working.
“We need to let the people decide on the next actions and we do that through a citizens’ assembly.”
Police officers could be seen surrounding the demonstrators and had earlier led a singing crowd of them out of the Parliamentary estate.
A House of Commons spokesman said: “We are aware of an incident on the parliamentary estate and are currently dealing with the situation as a matter of urgency.”
The Commons and Lords are in recess until Monday.