Pickers were able to start working the Morecambe Bay cockle beds on 1 September, a site where the deaths that sparked the crackdown occurred two years ago. The eagle eyes of the authorities, including the Gangmasters Licensing Authority (GLA), were out in force checking licenses.

Anybody who supplies workers to the agriculture, shellfish gathering and food and drink processing and packaging sectors in the UK needs to be licensed by the GLA, or they risk prosecution and imprisonment of up to 10 years.

As only five shellfish gangmasters out of total of 80 currently hold licences the GLA said it assumed that some gangmasters had tried to operate illegally.

The GLA was set up to curb the exploitation of workers in the agriculture, horticulture, shellfish gathering and associated processing and packaging industries.

It has been an offence to supply labour to the GLA regulated sectors since 1 October 2006, with the maximum penalty being 10 years imprisonment and an unlimited fine. It has also been an offence to use labour supplied by an unlicensed gangmaster in the

GLA regulated sectors since 1 December 2006, with a maximum penalty of six

months imprisonment and a £5,000 fine.

Five shellfish gangmasters currently hold a GLA licence and a further two licences applications are being processed.

In August alone, the GLA revoked 13 licences held by labour providers for breaches to the requirements, including the poor treatment of their employees or for using illegal workers.

The law also requires workers to be paid at least the minimum wage.

The European Commission is currently looking at implementing a similar crackdown on companies that use illegal labour. The Commission has proposed a series of sanctions - including criminal prosecution - against companies that continually break illegal labour laws.

The proposal mirrors new laws in the UK aimed at cracking down on the use of illegal labour in the agriculture and food manufacturing sectors. A similar EU-wide law would expose managers across the bloc to fines and possible jail time.

The Commission is proposing an EU-wide requirement that all employers undertake specific checks before recruiting a third-country national and notify national regulators

Employers who cannot show that they have complied with those obligations will be liable to fines and other administrative measures.

Member states would be required to pass laws imposing criminal penalties against those who have repeatedly infringed the law, who are caught employing a significant number of illegal labourers, who operate using exploitative working conditions, or if they know that the worker is a victim of human trafficking.

The number of illegal migrants employed in the EU range between 4.5 and eight million, increasing by up to 500,000 per year, according to Commission estimates.