The report, which has been published by University of Hull academics to coincide with the bicentenary of the legal abolition of slavery in the UK, highlights the hidden use of modern slaves by the food and other industries.

It found many UK companies relied on people working in slavery conditions because it is cheap and dispensable.

Current protection and support services for trafficked men, women and children is 'inadequate' and there is no specific assistance available to those who are trafficked for labour exploitation, according to Anti-Slavery International, which co-produced the report.

During pilot research, Anti-Slavery International identified 27 cases of migrant workers who were trafficked for forced labour in the UK, with victims originating from European, African, South American and Asian countries.

Case studies featured in the report highlight how food processing and packaging firms are using forced labour to meet production demands, despite recent legislation against the practice.

The UK has introduced the Gangmasters Licensing Authority (GLA), which was created to prevent exploitation of illegal workers in the agriculture, horticulture, shellfish gathering and associated processing and packaging industries.

From 1 December 2006 it has been illegal to supply workers to the agriculture and food processing and packaging sectors without a GLA licence.

Anybody who still uses an unlicenced labour provider operating in farming and food processing sectors is committing a criminal offence and faces up to six months imprisonment or a £5,000 fine, or both.

However, the report says that the majority of the people identified had entered the UK legally, but were made to believe they were illegal by the actions of traffickers in order to control them.

Workers with valid visas are subject to more subtle threats because the ownership of work permits resides with the employer and not the employee. The balance of power, the report says, means that companies can exert their demands on employees who have little choice to comply or face extradition.

The report says the vast majority of people trafficked for forced labour and exploitation are generally not identified as there is insufficient awareness or training among the relevant agencies and individuals.

The report also notes that since the 2004 Asylum and Immigration Act, there has yet to be a single prosecution brought for trafficking for labour exploitation.

Last month, Prime Minister Tony Blair announced that the UK would sign the Council of Europe convention on action against trafficking in human beings, which guarantees a minimum level of protection for victims.

Amnesty International, Anti-Slavery International and UNICEF UK welcomed the move, but urged the government to ratify and implement the Convention to the highest standard as a matter of urgency.

The slavery report says it is equally important that governments, including the UK, provide guaranteed protection and help to all trafficked people.

It claims that there is a tendency to see trafficked people as illegal immigrants involved in a criminal offence rather than victims of a crime.