Organised criminal gangs which force illegal migrants to work in poor conditions for a few pounds a day could be operating in Leicestershire.

UK Border Agency officials yesterday searched lorries for illegal immigrants at Leicester Forest East services, on the M1, as part of a national operation.

Officers said many of the illegal immigrants would end up virtual slaves, trapped into paying off the fee – which could be several thousand euros – for being smuggled into the country.

Many workers would be forced to work for a few pounds a day – and have much of that deducted by bosses and traffickers.

Phil Dyer, a senior manager from the agency's immigration team at Castle Donington, spoke during the operation at Leicester Forest East.

It was part of a nationwide crackdown at 27 sites across the country, codenamed Operation Mermaid.

He said: "This is the extreme end of things where people are being treated like modern-day slaves, working in poor and dangerous conditions for long days and coming out with very little money.

"It is exploitation at the highest point of the scale.

"We have recently prosecuted a firm in Derbyshire and we know it goes on elsewhere in the East Midlands."

He said the most unscrupulous employers charged workers to use the tools they needed, for accommodation and, in some cases, fined them for spending too long in the toilet.

He said: "These people then find themselves trapped in a debt bondage.

"They can't leave because they don't have the money, because they fear possible repercussions and they have no one to turn to."

Border agency officers used the operation to gather intelligence from drivers and catch up with haulage companies, which had been caught carrying illegal immigrants but not paid fines.

A number of drivers were detained.

Immigration minister Phil Woolas MP visited the Leicestershire operation.

He said it reminded haulage firms of their responsibilities, and the penalties.

He said: "It also serves to hammer home to would-be illegal migrants and organised smuggling gangs that we will catch them."

No stowaways were found yesterday, but last year 31 Leicestershire businesses were raided, resulting in penalties totalling £430,000.

Between last April and January this year, 76 illegal workers were arrested during 36 raids in Leicestershire.

Mr Dyer said: "Quite clearly, there's a duty on us to make sure we are removing illegal workers from employment in order that local workers get the opportunity to take these jobs."