During the investigation, the BBC team met one of the agents, named Vicki, who was open about the fake documents he could obtain, and boasted about customers as far afield as Sheffield, Bradford and Coventry. Vicki said he could get people into the country on lorries, known as donkeys, organised by what he called his "man in Paris", and told how he could provide a fake "original" passport that had been "checked" to beat security at a UK airport.

When Vicki was later confronted with the details of what had been filmed, he denied doing anything wrong and said it was a case of mistaken identity. The BBC team met Indian employers who said they had no problem obtaining papers for the illegal workers, some of whom were willing to shell out huge sums of money for fake passports. There were Indian landlords renting out space to the "faujis". And, there was no shortage of work, though the workers are grossly underpaid.

The undercover team found there was no shortage of job offers, including at a Southall chip shop where a "fauji" told of being employed for 12-hour days, six days a week at £150 - about £2 an hour.

One BBC reporter, Mohammed, went there for work. The owner, Bhupinder Singh, said to "never mind" the fact he had no papers, that he would "handle that issue" and that the reporter should not mention it "otherwise you may be nicked". Another time Mohammed went to an area well known to Southall "faujis", where they wait at the roadside to be picked up for casual labour. A man approached and a job "interview" was conducted.

"Do you want work?"

"Yes."

"Come on then."

Mohammed was taken to a building site and, without being asked whether he had any experience, was put to work on a roof parapet with no training, safety advice or kit. He was paid £35 for 12 hours' labour.

The BBC says of its expose: "One clear fact remains: the scale. In just one square mile, hundreds of illegal immigrants, scores of multiple-occupancy houses, and people dealing in fake identities, employment and fraud. A criminal network that is out of sight."

This is the second major expose of the illegal Indian immigrant network in Britain. Last year, an independent Indian film maker, Savyasaachi Jain, released a documentary in India and Britain, titled "Shores Far Away", on the subject. Jain filmed extensively in Britain and parts of eastern Europe to document the illegal migration route from India. In Britain, the film showed the network and the "faujis" at work in London, Birmingham and Leicester.

The documentary was screened in London, Leicester and Glasgow. Leicester East MP and member of the parliament select committee on home affairs Keith Vaz, who watched the short film had admitted: "Illegal immigrants are trafficked by these smugglers from India via Russia, the Ukraine, Turkey and then on to Calais (France) from where they reach the United Kingdom and cities like London and Leicester. Another route for the illegal immigration is through Russia, the Ukraine, Slovakia and then into Austria, the gateway to western Europe."

The BBC expose comes at a time when the British government is strictly enforcing laws against illegal migration, particularly from Asia. In February, Home Secretary Jacqui Smith announced the introduction of local immigration teams across the UK by 2012 to prevent businesses employing illegal workers.

Businesses will also be named and shamed on the UK Border Agency website, and those who continue to break the rules will face huge fines, upto £10,000. Since then, enforcement officers have raised hundreds of Asian restaurants, detecting hundreds of illegal workers from India, Pakistan, Bangladesh and south-east Asian countries.

This exercise comes in the wake of the introduction stricter immigration rules and protests by various British groups about the negative impact of illegal immigration on the local population.

In January, 2004, India and Britain signed an agreement to formalise sharing of intelligence to combat terrorism, and to allow Britain to send illegal immigrants back to India more easily. "The re-documentation and the ability to deal with this issue is indicative of the tremendous strides we have taken together," then home secretary David Blunkett had said after the signing of the agreement.