The London Olympics will be a magnet for people traffickers smuggling sex slaves and illegal workers into Britain, Home Office and police chiefs forecast yesterday.

Investigators believe that gangs are certain to try to exploit the millions on offer for workers on the £9 billion project. The gangs know that workers will have wages to spend.

The warning came in a Home Office report on combating trafficking, published yesterday, which noted: “Criminal elements are expected to exploit the situation by establishing themselves in London from now on. Organised immigration crime, including human trafficking, has been factored into the strategic planning for the Olympics 2012.”

Graham Maxwell, the deputy chief constable of South Yorkshire and a national spokesman on combating trafficking, said: “There is a possibility for labour exploitation and a possibility for sexual exploitation. There will be huge construction projects taking place.”

He added: “You will have young men together who earn considerable amounts of money. If they spend that money paying for sex, we must make sure they are aware there are women held against their will. Organised crime will operate wherever they can make a profit.” As part of the strategy, freed victims of trafficking will be allowed to stay in Britain temporarily and the Home Office is accepting the European Convention on Action Against Trafficking in Human Beings.

The convention offers victims such as women sold into the sex trade the right to at least 30 days’ grace after they escape from traffickers.

Ministers have until now refused to join the agreement because there were fears that it could be abused by illegal immigrants and even attract illegal immigrants to Britain.

The move is likely to win cross-party backing after the Conservatives urged ministers to sign the convention earlier this year. David Davis, the Shadow Home Secretary, said that the step was vital for “moral reasons” in an effort to protect exploited victims.

There were an estimated 4,000 victims of trafficking working in prostitution in the UK during 2003. Another estimate put the figure at 10,000 in London and the Midlands.

Other aspects of the plan include special teams set up at ports, a new national system to support victims and a child trafficking telephone advice line.

John Reid, the Home Secretary, signing the convention yesterday, said: “This weekend marks the 200th year since the legal abolition of the slave trade and I am happy to celebrate such an occasion by taking steps forward to tackling the appalling modern-day slavery we see in human trafficking.”

He said that the convention would help Britain to give minimum rights and protection for all identified victims of trafficking.

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