Demonstrators opposed to expansion at Stansted airport have attempted to storm the Houses of Parliament while the Lords voted on the terror bill.
Police have blocked the St Stephen's Gate entrance to Parliament with wooden bars as a group of protestors attempted to enter the building at the public entrance.
Reports from the scene have suggested some of the protestors are dressed up in costumes, in honour of the anniversary of the Suffragettes' rush on Parliament.
Demonstrators are also holding banners protesting against airport expansion.
Metropolitan Police said a group of demonstrators gathered within Parliament Square at about 18:10 BST and approached the St Stephen's Gate entrance of the Palace of Westminster.
In a statement, the police said: "Police were aware that this group intended to lobby their MPs, as is their democratic right.
"On arriving at the St Stephen's Gate entrance the crowd attempted to rush the entrance.
"A pre-deployed line of police officers prevented this from happening. Additional officers were put in place to start to disperse the crowd from the Palace of Westminster.
"None of this group gained access to the Palace of Westminster. Police are working with the Palace Authorities to ensure that the democratic working of Parliament is not impeded."
At the time of the protest, the House of Lords was voting on the governmnet's Counter Terror Bill.
The bill was voted down by the House and has been sent back to the Commons.