Organisers of a protest camp opposing a new detention centre close to Gatwick Airport have accused Surrey Police of "playing a dirty war" against them.
Protesters say they are unhappy at having to change camp sites
The group, No Borders, had been given permission to be based in a rented field near Salfords, in Surrey, for the six-day event starting on Wednesday.
But it said police put pressure on the farmer to change his mind, forcing the camp to move to Balcombe, West Sussex.
Police denied harassment and said they were given short notice about the camp.
No Borders spokesman Ian Bros said the group was unhappy it had to move from its original site.
"It fitted our needs - it had better public transport... and we've lost money on having to change the site," he said.
But Supt Alan Sharp, of Surrey Police, said: "We are stretched at the moment with foot-and-mouth and other things through the summer, and the ratepayer of Surrey pays our wages.
"If this impacted on our ability to police much more critical incidents in Surrey then I think the ratepayers will be asking us why."
The group, which is against all forms of immigration control, is planning to hold peaceful demonstrations against the siting of a second asylum seeker removal centre near the airport.
The Home Office plans to open the 420-bed detention centre, Brook House, in 2008.
It will be close to the existing centre, Tinsley House, which currently holds 135 people.
Organisers of this week's protest are planning to hold demonstrations in Crawley, Gatwick and Croydon, south London.