Members of climate activist group Extinction Rebellion on Friday glued themselves to the Speaker's chair in the UK House of Commons, calling for a "Citizens' Assembly" to help shape environmental policy.

"Just before noon today (1100 GMT), a group of around 50 people took nonviolent action at the House of Commons," the group said in a statement. 

"The parliament action began with three people booked on an official tour of the building, gluing themselves in a chain around the Speaker's Chair." 

The group, wearing t-shirts reading "Let The People Decide", took it in turns to read a speech calling for a Citizens' Assembly to "give ordinary people a say over the major crises facing us." 

Parliament is currently on summer recess, with politicians due to return on Monday.

Outside parliament, another member climbed up scaffolding around the Elizabeth Tower housing "Big Ben" and raised a banner reading "Let The People Decide - Citizens' Assemblies Now".

Two others chained themselves to the railings. 

"To create a new, fairer politics will require first thousands, then millions of us," said Alanna Byrne, of Extinction Rebellion. 

"It will require sustained culture-shifting civil disobedience, until we become impossible to ignore."

The group has carried out multiple actions over recent years, including blocking motorways and London roads, with some activists receiving jail terms.

It called Friday's action "the opening act" of its September plans, which "will act as a launch event for a five-phase plan to bring 100,000 people onto the streets in civil resistance next spring."