Many young women are forced to work as prostitutes

Sir Stephen Lander told the Times newspaper illegal migration was potentially "very troublesome" and a harder problem to tackle than drugs.

Thousands of women and children a year are smuggled into Europe and exploited for sex and cheap labour.

The bill creating Soca faces its second reading in the Commons this week.

The government has already announced it will focus on confronting organised criminal networks which make an estimated �40bn a year.

I looked after three children, cooked, cleaned, did all the domestic tasks. I received no payment Dayo - trafficked to the UK from Nigeria 'I was a victim of child traffickers'

Soca will have about 5,000 staff, to whom it will be able to designate the powers of police, customs and immigration officers - although they will not work for any of those groups.

Sir Stephen told The Times: "Drugs is the most immediately impactful [crime], but there is a sense that illegal immigration is potentially as big a problem for the UK.

"This is a very troublesome potential for the country. We are a very attractive target for people who wish to make money out of [the] desire [of] ordinary human beings to better themselves."

The Home Office says key "transit regions", from which people are smuggled, include the Western Balkans, West Africa and parts of Cambodia, China and Vietnam.

Bill Hughes - head of the National Crime Squad will lead Soca, with former MI5 chief Mr Lander as its chairman.

Sir Stephen was reluctant to talk about specific tactics - a Home Office spokesman said dealing with serious organised crime was "not simply about prosecution and conviction" but about finding new approaches.

Criminalising trafficking

"We need to use all of the intelligence available to us to read the market and we need to start introducing some restrictive practices into the criminal environment," said the spokesman.

He added that new laws had been introduced to "comprehensively criminalise" trafficking, including a maximum 4-year jail term for those convicted of trafficking for sexual offences and a new offence of "trafficking for exploitation".

Organised immigration crime taskforce Reflex, of which Mr Hughes is head, has also helped disrupt gangs involved in human trafficking and people smuggling.

There were 38 convictions as a result between April 2003 and April 2004, says the Home Office.