Parliament Square peace protesters were threatened with court action today unless they clear their makeshift camps from the pavement area by the end of the working week.
Westminster Council in London said it would seek a High Court injunction forcing the campaigners to stop obstructing the pavement if they did not clear tents, boxes and placards away by 5pm on Friday.
Council staff were accompanied by Metropolitan Police officers as they served about 30 people with legal letters today.
The letters said the camps were stopping ordinary workers and tourists from going about their daily business.
They said: "The council has become increasingly concerned about the number and size of the structures which have been deposited on the public footway in Parliament Square, particularly since the Mayor of London obtained an injunction in the High Court authorising removal of the 'Democracy Village'.
"The structures in question include all tents, box structures and placards which have been placed and erected and are being maintained on the public footway in Parliament Square.
"Although the council recognises all individuals' right to protest peacefully, it is considered that the extent and manner of the protest has a disproportionate effect on amenity and the rights of the public to the use and enjoyment of the public highway."
Anti-war protesters were forcibly evicted from the grassy area of the square in July after losing a Court of Appeal battle to stay. Lawyers for Mayor of London Boris Johnson argued the square was an open space which the public had a right to use.
Under the 1980 Highways Act it is an offence to wilfully obstruct a public highway and anyone found guilty can be fined up to £1,000.
The courts also have the power to order the removal of any obstruction which remains in place after conviction and issue a further fine of up to £5,000.
Peace campaigners have defended their right to free speech and assembly and in 2002 veteran protester Brian Haw won the right to maintain his camp on the pavement after the High Court ruled any injunction would be an unreasonable breach of his human rights.
Mr Haw's tent now occupies a corner of the gardens, outside the area which was fenced off in the summer, and he was not handed a legal letter today.
But the council said the overall situation was "significantly different" from nine years ago.
Council leader Colin Barrow said: "We've been pressing the Government for some years to end the blight of Parliament Square by enacting legislation which we, along with all the relevant authorities, can use to end the current mess.
"Today's action is the first step in a process that we hope will end the ludicrous and unacceptable situation around the square.
"As the local highway authority we have a duty to ensure that our pavements and walkways are free for all people to use - particular those opposite the Palace of Westminster.
"I would like to stress that we have nothing against peaceful protest - Westminster has a long and proud tradition of hosting dozens of major protests and demonstrations every year.
"But it is simply wrong for our pavements to be turned into no-go areas and permanent protest campsites by vociferous minorities - regardless of how laudable their particular cause may be."
The council wants powers to tackle protesters, prevent permanent encampments and ensure that people who are moved on cannot just decamp to other areas.