Eviction notices have been served on residents at what is believed to be the biggest unauthorised travellers' site in the UK.
Basildon Council has given travellers occupying 51 unauthorised pitches at Dale Farm, Essex, 28 days to vacate the land.
Tony Ball, leader of the council, said: "It is very disappointing that we are in this situation, as for years we have attempted to work with the people living on this unauthorised site to seek a peaceful resolution."
Eviction notices were served on Monday after the council last week agreed a £1.2 million contribution towards the cost of policing the clearance. The Government had already agreed to contribute £1.2 million.
If the travellers do not leave, the council will enter the land and remove all portable and fixed structures, hardcore and hard standings from the greenbelt site where breaches of planning law have taken place, said a statement.
More than 400 travellers live at the former scrapyard which is on greenbelt land and about half of the 100 pitches do not have planning permission. Traveller families began to settle on the site 10 years ago.
Mr Ball said: "It is important to remember this is a greenbelt site and this development is not legal. The law must be upheld equally and fairly in all cases and the council has made clear, for more than 10 years, its intention to clear this site and return it to a condition in keeping with its greenbelt status.
"I have become increasingly concerned that a number of campaigners are giving poor advice to the travellers at Dale Farm, leading them to pursue continual challenges rather than urging them to make preparations to leave.
"I believe this has given the travellers false hope as it has made them believe a last-minute legal ruling could stop the site clearance. I feel these campaigners are doing a great disservice to the people they are attempting to help.
"As a result, over the years few people on this site have accepted our offers of help. That said, there is still absolutely no reason why children, the elderly or vulnerable should end up on the roadside."