A GIPSY activist openly told how the "slaves" were a focal point to some travellers' lives and how many families favoured "strong workers of low IQ".

Dr Donald Kenrick, an expert in Romany language who helped travellers turn green belt into permanent homes in Basildon and elsewhere, described the practice as "very common".

He said: "Dossers are people gipsies pick up to work for them. They are sometimes called slaves or servants.

"It is common among Irish travellers, but the English do it as well."

Mr Kenrick said travellers favoured single men, who were strong workers, but of poor mental health.

He said: "They sort of adopt them, so they become part of the family.

"They will usually find them in hospitals when they have no other relatives and nowhere to go."

Mr Kenrick argued the practice meant otherwise vulnerable people were being cared for.

But he also said if a dosser became too old to work, he may become a burden, and the family may get rid of them. He said: "Some stay for many years and I have done planning applications, where they will request a separate caravan for the dosser to live in.

"They are increasingly recruiting Polish people nowadays and even Polish Romanies."

Mr Kenrick admitted if dossers were paid, it was unlikely they would pay income tax, but disputed they were held against their will. He said: "There is no reason why they should be.

"If he got too familiar with the women, he may be kicked out, but most welcome having a home, food and family and some stay for 10 to 20 years."