Twenty-four modern day slaves have been released from bondage after a pre-dawn police raid found them emaciated, hungry and living in ''filthy and cramped'' conditions at a British caravan park.

The men - Poles, Romanians and Russians as well as British - had been forced to survive in a ''state of virtual slavery'' at the Greenacre caravan park in Leighton Buzzard, north-east of London, according to police.

The men varied in age from about 20 to 50; all were vulnerable and had been recruited from homeless shelters and dole queues. Some are believed to have been in virtual captivity for up to 15 years. Five people - four men and a woman - were arrested in the raid on the mainly gypsy site at 5.30am on Sunday. The raid involved 200 officers.

Detective Chief Inspector Sean O'Neil said the men had not been paid for physically demanding labouring jobs, were hardly fed and were given no clothes. If they complained they faced beatings.

''The men we found at the site were in a poor state of physical health and the conditions they were living in were shockingly filthy and cramped,'' he said.

Police said some of the men would have to be carefully reintroduced to a proper diet.

''This was a recruitment centre where people down on their luck were brought to,'' Inspector O'Neil said. ''They had been found in soup kitchens and benefit offices and told they would be given work, clothing, a home and food.''

When new recruits arrived they would have their mobile phones confiscated and their heads shaved: ''They were told by the people who had brought them here 'You have no family now, we are your family'. If they wanted to leave they were threatened.''

A police spokeswoman, Jo Hobbs, said the men lived in unsanitary conditions.

''There were up to four men living in tiny and filthy caravans which were unheated, and old,'' she said. ''They had no access to running water, no toilet and no washing facilities.'' The men were thought to have worked from 7am until 7pm most days.