The laws which restrict the right to demonstrate in Parliament Square need to be changed, Gordon Brown has said.
The Lib Dems have campaigned against the law
The PM said change was needed to balance "the need for public order with the right to public dissent".
He said he would consult with police, Parliament, civil liberty groups and Westminster council.
A 2005 law created an "exclusion zone" inside which all protests required police permission. Critics say it curbs the right to spontaneous protest.
The requirement for police permission was introduced in the Serious Organised Crime and Police Act 2005.
It was partly a response to anti-war protester Brian Haw, whose round-the-clock vigil in Parliament Square, using placards and loudspeakers had annoyed MPs and peers.
The Home Office has also said the law was necessary for security reasons - it had been argued that a bomb could be left beneath Mr Haw's signs.
But while Mr Haw remains in the square, having been granted police permission for a reduced protest, many other unauthorised, peaceful, protests have been broken up.
The restrictions have been heavily criticised and the subject of several unauthorised protests themselves.
In January Lib Dem Baroness Miller said the 2005 Act had had a "chilling" effect on demonstrations, as many people believed they were totally banned.