Media playback is unsupported on your device Media caption The BBC's Paul Kenyon goes undercover to investigate gangs smuggling migrants out of Britain

Illegal immigrants fleeing the authorities in Britain are paying criminal gangs to smuggle them out of the UK, the BBC's Panorama programme has found.

The migrants are charged as much as £1,500 for the chance to be taken to mainland Europe.

Some want to try their luck elsewhere in the EU instead of going to their home country, others are criminals.

The government said it is cracking down on organised immigration crime.

Using secret filming, Panorama reporter Paul Kenyon posed as a migrant from Moldova, which is outside the EU, who had no passport or documentation and who needed to leave the UK.

Disillusioned migrants

A gang member told the reporter he would be smuggled out to the French port of Calais in the back of a lorry with three or four others. The price for passage would be £1,500.

The man said the gang makes two or three similar trips a week and smuggling illegal migrants out of Britain is much easier than breaking in to the country.

The programme found three other gangs operating similar networks.

When Kenyon arrived at the appointed time to meet the smugglers, he and another man from India were driven through London's rush-hour traffic for two hours. They then reached another car that was to take them to meet a lorry bound for France.

The fellow passenger told the reporter that he was an illegal migrant to the UK and the increasing demand for documentation was the reason why he wanted to try to reach Spain and try life there.

The BBC was not prepared to hand over any money to the smugglers and confronted the man who had arranged the trip. The man, known as Munga, denied taking money in exchange for people smuggling.

Mark Harper, Minister of State for Immigration, said Britain is working with other European governments to tackle criminal gangs involved in the movement of migrants.

"One of the things we do with our colleagues in other, both EU countries and non-EU countries, is work closely internationally to try and crack down on these gangs who are committing organised immigration crime and preying on some of these vulnerable people."

'Ghosts'

Panorama: Find out more Paul Kenyon presents Immigration Undercover

BBC One, Monday, 21 January at 20:30 GMT Then available in the UK on the BBC iPlayer

There are no firm figures on the number of illegal migrants living in Britain, although in 2009 a London School of Economics study reported that there were at least 600,000.

The so-called "ghosts" are a mixture of failed asylum seekers who have not returned home and economic migrants living and working illegally in the UK.

Many first came to the UK on bogus students or tourist visas and overstayed in order to work.

In 2009, of all the non-EU students who came to Britain, the National Audit Office estimated that one in six - or between 40,000-50,000 - worked illegally instead. These bogus students led the government late last year to bar more than 500 colleges from taking non-EU foreign students.

Refugee support groups say migrants living beneath the radar are often driven by fear.

Dave Garratt from Refugee Action said in some instances, legitimate asylum seekers are having their claims rejected and are being driven to desperate measures.

"We see clients every day who are prepared to take up prostitution rather than return, prepared to take up criminal activity rather than return. In some cases prepared to take their own lives rather than return home," he said.

Panorama: Immigration Undercover, BBC One, Monday 21 January at 20:30 GMT and then available in the UK via the BBC iPlayer.