French police this morning began clearing an improvised camp dubbed "the jungle" where migrants gather near the port of Calais before trying to cross to Britain.

The operation, announced last week, has been heavily criticised by humanitarian groups who say it will do nothing to solve the problem of illegal immigration, but Immigration Minister Eric Besson defended the move.

"I want us to dismantle this camp which is a base for people traffickers," he told RTL radio shortly after the operation began. "There are traffickers who make these poor people pay an extremely high price for a ticket to England.

"This is not a humanitarian camp. It's a base for people traffickers," he said.

He said around 250 people had been in the area on Monday but he was unaware of how many were still there as police moved in.

The makeshift tent city grew up after France closed a large Red Cross centre at nearby Sangatte in 2002 under pressure from Britain, which saw it as a magnet for clandestine immigrants.

Humanitarian groups say the high-profile closure of the "jungle" will merely move the illegal immigrants elsewhere in the area.