Over a third of those supplying mainly foreign workers to Northern Ireland’s farming and food industries could be exploiting them, an oversight body warned today.
Some bosses may be behind "shoddy and potentially lethal" practices, a trade unionist claimed.
In one case, inspectors discovered a van used to carry workers to their place of work which could have become a death trap in an accident.
Gangmasters Licensing Authority (GLA) chairman Paul Whitehouse said: "It is unacceptable that the food you eat could have been picked, packed or processed by an exploited worker."
A gangmaster supplies labour to agriculture, food processing and shellfish gathering companies among others.
Peter Bunting from the Irish Congress of Trade Unions (ICTU) added: "There must be a rigorous campaign of public information directed at not only employers, but also people working for gangmasters, so that they can challenge the shoddy and potentially lethal practices of some bosses."
In one example, according to the GLA, a van used to carry workers was not designed to carry passengers and could have become a death trap in an accident. The additional cab had no seat belts fitted and no means of escape should the lorry have turned on its side. There was also no heating.
The study showed that a fifth of those who supply to regulated businesses had not heard of the GLA.
It said 63 per cent of agencies supplying to food processing and packing sector and 64 per cent for the farming and horticulture held a licence.
Other findings included that 14 per cent of agencies didn't know that a licence was required to supply workers into certain sectors, and a third wrongly believed a licence was required for massage parlours, casinos and certain nightclubs.
Those caught operating without a license face up to 10 years in prison but the farmers and food companies could also be prosecuted with up to six months behind bars.
The GLA began safeguarding the welfare of workers across the UK in 2006 and has already revoked the licences of 76 businesses in Scotland, England and Wales.
It was established following the death of 23 Chinese cockle pickers in Morecambe Bay.
Mr Whitehouse added: "Ignorance of the law is no defence, anybody operating without a licence must come forward immediately or face the consequences."
Mr Bunting called for better resourcing from the government for the GLA. "The levels of ignorance about the GLA from employment agencies in particular is shocking, if not surprising."
Bernadette McAliskey from migrant workers support organisation the South Tyrone Empowerment Programme (STEP) welcomed increased enforcement.
"The workers are the victims in this equation and need support and protection before and after the exploitation is exposed.
"GLA staff are, in our experience, sensitive to the importance of this factor in encouraging those suffering such abuse to come forward."
There are around 100 licensed gangmasters in Northern Ireland but the GLA doesn't know how many illegal operators there are.
Those tend to be smaller employment agencies, typically ones who pick people up in vans in an unregulated manner.
PA