More than 400 foreign children, many suspected of being trafficked into the sex or drug trade in Britain, have gone missing from local authority care.

Children from Africa, Asia and eastern Europe have disappeared from safe houses and foster homes around the country's biggest ports and airports, figures released to the Guardian under the Freedom of Information Act have revealed.

The missing children include at least 87 Chinese who disappeared from care around Heathrow and Gatwick and 68 from countries including Afghanistan, Albania and India who went missing from the care of Kent county council, which is responsible for protecting children trafficked through Dover and Folkestone.

Anti-trafficking campaigners believe the missing children are often taken from care by their trafficker and then exploited for prostitution, domestic servitude and other illegal activities. Other children escape out of fear of being found by the trafficker and without money or identity papers fall prey to further abuse and exploitation.

According to records from 16 local authorities around England's ports and airports, an estimated 408 children disappeared between July 2004 and July 2007. They are known by officialdom as unaccompanied asylum seekers and child protection campaigners believe most have been trafficked.

It is thought that many escape only for traffickers to send them on for exploitation in other parts of the world, particularly Italy and Spain. Only 12 children have been traced and returned to care.

"We are shocked that the numbers keep rising," said Christine Beddoe, the chief executive of ECPAT UK which campaigns for greater protection for trafficked children. "These figures come in spite of the government's action plan on trafficking and show the need for an urgent inquiry into separated children who go missing. These vulnerable children need to be given independent guardians as soon as possible to ensure they are protected from traffickers who we know target them even while they are in care."

Today local authorities on the front line of the illegal trade in children will tell ministers they need at least another £30m to continue offering the basic protections for unaccompanied asylum seekers under 18. ECPAT UK also wants the government to appoint an independent "rapporteur" who can work out the true extent of the problem. The last government estimate put the number of missing trafficked children at 183, which now seems low.

A spokeswoman for the Home Office said: "We are concerned about the number of children who go missing from local authority care each year who appear to have been trafficked. That is why we intend to identify a group of "specialist" local authorities which have effective procedures to keep children safe and to identify and provide proper services for the victims of trafficking. We intend to channel all cases to these authorities from around the country."

According to the figures obtained by the Guardian, Newcastle city council reported 12 Somali children missing and said 13 of the 17 Chinese children it has taken into care have disappeared. Officials at Suffolk county council said they find unaccompanied children arriving in shipping containers and in the backs of lorries travelling through Felixstowe. They admitted losing track of 16 children since March 2005, including six Afghans. The worst record was at the London Borough of Hillingdon which estimates it is dealing with 1,000 unaccompanied minors a year, coming mostly through Heathrow airport.

The council said 74 went missing between 2006 and 2007 and it does not know how many it lost in the previous years. Despite a system of safe houses for the 145 children who came into the care of West Sussex, which includes Gatwick airport, 42 went missing, largely Chinese and Nigerians.

"As soon as they can they will contact their trafficker," said Kirsty Hanna, manager of the Gatwick children's team. "It could be they have memorised the trafficker's mobile number, or the trafficker may have followed them to the safe house. There have been times when they have jumped out of the window. They are under a lot of pressure, often to pay back their passage. Their families back home could be threatened with torture or murder. We are constantly trying to disrupt the traffickers, but it has to be a losing battle if we can't stop the problems abroad that causes the trafficking."