They posted a photo of five people inside the chamber holding banners reading ‘Let the people decide’ and ‘Citizens’ Assembly now’.

The group also hung a large banner bearing the same words from scaffolding on the estate and protestors padlocked themselves to gates outside parliament.

Parliament is not currently sitting.

The House of Commons did not immediately have a statement. Certain areas of the parliamentary estate are usually open to the public, although access to the debating chamber is usually restricted to guided tours.

Extinction Rebellion, a group which has previously caused days of traffic chaos in central London, typically protest climate change issues.

They said the protestors were reading a speech which included the words: “We are in crisis. We can not afford to carry on like this.”

(Reporting by William James. Editing by Andrew MacAskill and Alistair Smout)