Airports are being used by people smugglers to hold "slave auctions" of women being sold into prostitution, said the Crown Prosecution Service.
Trafficked girls and women are often forced into prostitution
The CPS said traffickers were trading sex workers as soon as they arrived in the UK from countries, including states in eastern Europe.
"Brothel keepers are bidding for women destined for prostitution," it said.
Meanwhile the Sunday Telegraph reported hundreds of children as young as six are brought to the UK yearly as slaves.
'Coffee shop auction'
A CPS conference on Monday is to discuss airport crime, and its director in west London, Nazir Afzal, said: "Criminal activity at the UK's airports is on the increase.
"We are now seeing 'slave auctions' being held in public places at airports where brothel keepers are bidding for women destined for prostitution."
One auction had taken place outside a coffee shop in the arrivals hall at Gatwick Airport, the CPS said. Others were believed to have been staged at Heathrow, Stansted and other UK airports, it added.
Ministers earlier this year set out proposals to boost action against sex trafficking gangs.
In a separate report, the Sunday Telegraph said children from China, Vietnam and Malaysia had been found working in sweatshops, restaurants, and cannabis factories in Britain.
African children, it said, were often put to work in domestic service, putting in long hours for minimal reward, if any.
And children from eastern Europe were said to be used to beg and steal.
A consultation paper has been prepared for the Home Office by a coalition of nine charities including Unicef, Save the Children and the NSPCC.
The coalition, called End Child Prostitution, Pornography and Trafficking (Ecpat) has called on the government to do more to tackle child trafficking.
Ecpat research says child trafficking has moved from London to Liverpool, Manchester and Newcastle.