Migrant labourers working in food processing and packaging plants all over the country are sleeping on the premises, according to Fire Brigade officials. The shocking revelation is part of a string of abuse claims being investigated by both government agencies and the Fire and Rescue Services. This follows the blaze at the Wealmoor fruit packing warehouse that claimed the lives of four firemen this month.

The fire has brought to the public conscience the possibility of unregulated workforces being allowed to sleep on site, meaning nobody knows how many workers are inside in the event of an emergency. Though there was no evidence of improper working practices at Wealmoor, investigations are ongoing as firefighters entered the warehouse after rumours that workers were trapped inside.

John McGhee, Fire Brigades Union national officer for health and safety, believes the Wealmoor tragedy must be understood in the context of alarming working practices that are being uncovered across the country. "There are unscrupulous employers allowing people to sleep in their factories. If people are working or sleeping on site without full regard for or understanding of fire and safety procedures then it becomes a big issue for my members when we arrive at an emergency."

A source from the Gangmasters Licensing Authority, the government body investigating exploitation of workers in the food industry, refused to rule out the possibility of workers 'sleeping on the job'. The source said the GLA finds all sorts of abuses and exploitation occurring in factories belonging to some of the UK's top names in food: "I would never say this doesn't happen, it is just about finding hard evidence. Many food factories are in rural locations, so accessibility and transport may be an issue at times. But if we were to find workers sleeping on the floor of food factories we would treat the matter very seriously."

The revelations back up the discovery by The Grocer that unskilled and untrained workers are being drafted into factory positions by the truckload, predominantly from the EU accession states, without any health and safety training or adequate safety kit. Many, especially those with poor English, are too scared to speak out about the conditions they work in, the poor housing they live in and the illegal deductions that regularly show up on their wage slips.

A factory worker, after witnessing the disturbing changes that have taken place at her food plant, approached The Grocer with incriminating evidence. Katie (not her real name) has worked at her factory in England for almost two decades. It belongs to a well-known name in the food industry that supplies a number of supermarkets and has been flooded with Polish workers whose treatment, she says, has been "horrendous". She says about half the 350 staff are now new on the workforce, having been placed there by a local recruitment agency.

Worryingly, according to Katie, the agency workers are often so in need of extra money that they almost never refuse overtime. "This makes it very difficult for anyone to keep a proper record of who is doing what at any time of day. I don't even know if they are on the fire register," she adds.

"There have been accidents," Katie says. "One or two falls but nothing serious yet. Every day I see a new accident waiting to happen but all the safety warning signs and the signs telling people what to do in case of injury are in English. Many of these workers don't speak more than a word of English - yes."

Katie says her new co-workers get no training to do skilled jobs. "They are told to operate heavy machinery and look to us for help. All we can do is communicate in sign language. Some, who can speak a little English, have told me they had no induction.

"To work in a room with a high volume of particles in the air, you have to wear a special mask. If you aren't shown how to use it properly you can have trouble breathing and I've seen some who have had terrible reactions ."

According to Ian Hodson, a regional officer for Bakers Food and Allied Workers' Union, many foreign labourers being used don't even know what the fire alarm at their place of work sounds like. Hodson, currently working on disputes and grievances with a number of top food manufacturers, says: "Individuals tell us they have had no training at all and don't understand any of the safety literature thrown at them on day one. Some are being charged for their own protective equipment while others aren't being given safety equipment at all.

"We've had instances of 'new working arrangements'," says Hodson, "which basically means managers make a large number of staff redundant and replace them with agency staff, mostly originating from Eastern Europe."

The Gangmasters' Licensing Authority, set up in 2005 to curb exploitation of workers, admits it is struggling. "Anyone who supplies workers into industries, whether they be high street recruitment agencies or sole traders with a van, can be labelled gangmasters," says a GLA spokeswoman. "We ensure they meet all requirements and grant licences, which cost £2,000 for any gangmaster turning over less than £1m. But receiving a licence just means the recipient met standards at one moment in time. We can return a week later and find all sorts of abuse occurring."

The source says the GLA commonly finds labour providers taking illegal deductions from salaries. These are taken for transport and accommodation that is often inadequate. "You see a lot of 'hotbedding'. This is where too many workers, often migrants, live in unsanitary conditions in houses of multiple occupancy. They often work in dangerous conditions without proper training but we struggle to find out because many labour providers get our licence to give themselves a veneer of respectability. Their priority having got a licence is to get workers into their factories without care for their welfare or rights."

The GLA has the power to revoke the licences of convicted offenders and can press criminal charges against those acting without a licence. One prosecution is going through in Scotland but since the GLA got its powers last year few arrests have been made.

"Workers are often scared to reveal the truth and want to avoid trouble," the source adds. "Even though there may be evidence of verbal and even physical abuse along with deductions from their wages, some of them have different cultural expectations of work and may not understand they are being wronged."

Another source said: "Though it would be wrong to pass blame on anyone above and beyond the labour provider and the employer, it could be noted that the multiples putting constant pressure on suppliers to keep costs low have an indirect impact on the labour suppliers employ."

An executive at one of the UK's top labour providers insisted most agencies provide "generic" health and safety and food hygiene information but admitted: "It is up for debate as to who is responsible for full health and safety training for each job, us or the employer."

In this murky world where responsibility is passed from one to another like an item on a conveyor belt, the problem continues.n