Attempts to ban an anti-war march in London will boost the numbers of those attending, organisers have said.
Demonstrators at an anti-war protest in February
The Stop The War Coalition (STWC) is planning a march to parliament on Monday calling for a withdrawal of British troops from Iraq.
Scotland Yard has said the march cannot go down Whitehall because of an ancient law protecting the right of MPs and Lords to get to Westminster.
Police were "creating an unnecessary problem" said Lindsey German, of STWC.
A Metropolitan Police spokeswoman said it was in dialogue with the group to "facilitate a lawful demonstration" but a route has yet to be agreed.
She said: "Our aim is to balance the right of the STWC to freedom of protest whilst maintaining the right of MPs and peers to conduct the business of either House whilst they are sitting."
'Assault on democracy'
Ms German said publicity over the ban had generated more interest in Monday's march, which starts off with a rally in Trafalgar Square.
Prominent peace campaigners and MPs are expected to join the march, including Tony Benn, musician Brian Eno and comedian Mark Thomas.
Ms German said: "We are determined to go ahead with our march down Whitehall and we hope that even at this late stage the police will realise they are creating an unnecessary problem.
"We have had calls from pensioners, including a 78-year-old man, saying they are determined to take part in the march because of the attempt to ban it."
Labour MP John McDonnell said the attempt to ban the protest was "an unacceptable assault on our civil liberties".
"I will be joining the march to exercise my right to protest at the continuing presence of British troops in Iraq," he said
Prime Minister Gordon Brown is expected to make a statement on Britain's involvement in Iraq to Parliament on Monday.