The report says the government has failed to confront abuses

Part-time farm workers are being exploited by so-called "gangmasters" who provide casual labour to the agriculture and horticulture industries, say MPs.

The gangs are often made up of workers from overseas, some of whom are illegal migrants, say members of the environment food and rural affairs select committee.

Many of these gangs who are picking crops and packing produce operate outside the law, according to a report by the select committee.

It is a disgrace that the government has failed to give priority to the issue of gangmasters David Lidington, Shadow environment secretary Worker's hope turns to tragedy

MPs are convinced supermarkets' dominance over suppliers have helped create an environment where gangmasters' illegal activity could develop.

But major supermarkets have defended their policies as ethical.

Price competition and short timescales for orders put pressure on suppliers - leaving little opportunity or incentive to check the legality of labour sources, claim MPs.

"The enforcement agencies are insufficiently resourced and lack the political backing to make a significant impact on illegal activity within the agriculture and horticulture labour market," they said.

Abuse cases

The report looked at serious incidents involving foreign workers, including a case from a Citizens Advice Bureau in Cambridgeshire in which workers had been housed in partitioned containers with no water supply.

Their contracts included an agreement to re-pay up to £1,000 if they left within six months.

Also a group of Portuguese nationals had been paid £3 each for cutting 1,000 daffodils, following deductions for housing and travel.

Citizens advice bureaux had been approached by workers who feared losing their jobs if they complained, it added.

CAB spokesman Andrew Seagar said the workers they saw were only the "tip of the iceberg".

Consumers demand low priced fresh produce round-the-clock

But consumers were also to blame for demanding low priced fresh produce round-the-clock.

The CAB has called for government and European Union action to inform members of their rights before they arrive in the UK.

Shadow environment secretary David Lidington criticised the government's inaction in dealing with illegal labour suppliers.

"This is a damning report. It is a disgrace that the government has failed to give priority to the issue of gangmasters," he said.

A Department for Environment, Food and Rural Affairs spokesman said the government recognised the seriousness of the abuse and was working with organisations to devise a code of good practice and accreditation system for labour suppliers.

Code of conduct

But operations director of a farm in Stretham, Cambridgeshire, Kier Petherick, said it was a "popular misconception" all growers used illegal labour to maximise profits.

"They come for two or three days then disappear, and you get new people. It's a constant battle with retraining."

He said teamwork, health and safety for workers and quality for the customer were more important.

"We couldn't function with gang labour," he added.

We are heavily committed to helping our suppliers in the sourcing of temporary labour Marks and Spencer

One Polish worker on the farm - which sees workers earning £5-6,000 in around 12 weeks - said he had worked there for two seasons and hoped to return next year.

"After a few years I will be able to buy a house in Poland. I have already bought a car from the money I earn here," he told BBC Breakfast.

A spokeswoman for Sainsbury's supermarket said the chain took the issue "extremely seriously", being the first supermarket to address it by working with the Ethical Trading Initiative (ETI) and to introduce a supplier code of conduct.

"We pride ourselves on having a good relationship with our suppliers and regularly visit them to monitor practices," she said.

Marks and Spencer also cited the progress it had made through the ETI and by requiring suppliers to implement the company's Global Sourcing Principles.

"Astounded"

"We are heavily committed to helping our suppliers in the sourcing of temporary labour.

"We currently provide suppliers with 'Guidelines on Best Practice of Employing Staff' to help ensure the labour they hire has controls in place with regard social compliance and legality of employment," said a spokeswoman.

It is also calling for a 'White List' of approved employment agencies that comply with stringent guidelines to ensure suppliers only use approved sources.

Tesco said there was clear and specific legislation in place to protect workers.

A statement from the retailer said: "We find the committee's report astounding. Tesco does not employ illegal labour, we would never ask our suppliers to do so, and never condone such action.