Campaigners against the detention centre took to the streets in April

About 400 people are expected to join the six-day camp, planned by a group opposing all controls at international borders, from 19 to 24 September.

The No Borders group claims immigration restrictions are racist and wants free movement of people across the world.

Sussex Police said illegal activity, or interference with airport operations, would not be tolerated.

Ch Insp Jim Reid said: "We certainly won't accept any interference with London Gatwick Airport and its operations, or any incursion there.

"And we won't accept and tolerate illegal disruption and illegal activity."

'Fair asylum system'

Ian Bros, a spokesman for the Gatwick Area No Borders Campaign, has said the camp will be peaceful.

"Workers who produce the goods in third world sweatshops, that are allowed to pass around the world freely, should themselves be allowed to pass around the world freely," he said.

In April, more than 100 people took to the streets of Crawley in a demonstration against the building of a second detention centre.

Tinsley House detention centre, at Gatwick, currently holds 135 people - the Home Office plans to open another 420-bed centre nearby in 2008.

The Home Office has defended the plan, saying detention is part of a fair and robust approach towards asylum.

A spokeswoman said the Home Office accepted that immigration was a complex and emotive subject and people had the right to protest but believed detention was an essential element of enforced removal.