One MP said the curbs on civil liberties would "make a dictator blush".
Self-proclaimed 'statue defenders' were filmed hurling glass bottles, fireworks and smoke grenades at police on Saturday.
A planned Black Lives Matter rally has been cancelled amid fears of clashes between groups.
Brexiteers partied in Parliament Square as the UK's 47-year membership to the EU came to an end.
'Democracy is an ongoing process, it is not a one-off event.'
Police were aware both protests had been planned for central London on Saturday.
The protest saw a giant blimp modelled on Boris Johnson fly in Parliament Square on Saturday.
Shadow foreign secretary is "recovering" after accident in Parliament Square.
As President Trump continues his second state visit with a banquet at Buckingham Palace, protesters took to Parliament Square for a people’s banquet.
The 20ft effigy is expected to appear above Parliament Square on Tuesday - the second day of the US president's London visit.
“We would like to thank Londoners for opening their hearts and demonstrating their willingness to act on that truth."
At least 750 people have been arrested since Monday, in what the Met called an "unprecedented" operation.
"Peaceful protest has a long, rich history in Parliament Square. Sad to see this action taken."
Nigel Farage and Stephen Yaxley-Lennon spoke as thousands marched to Westminster.
Demonstrators are demanding a final say on Brexit be put to the people.
The traffic around Parliament Square in London was momentarily halted by a group of women protesting against the pension age. The protesters were calling on the government to move the pensionable age back to 60. They say that thousands of women have been left in financial difficulties and even destitution because of a lack of information regarding the change.
"If people want to spend their Saturday looking at me in a yellow bikini they’re welcome to do so."
Three people were treated at the scene following the crash.
As the 'carnival of resistance' packs up for the day, the president flies to Scotland.