Clerics and police have expressed concern, and now the Olympics minister has - London could see a proliferation in prostitution and human trafficking during the 2012 Games.

Some have warned the Olympics could see a repeat of the ”mega brothels” set up in German cities for the 2006 World Cup in Germany.

Tessa Jowell said: “I am concerned about that. I certainly became aware of it in the run-up to the World Cup.

“We need to send the strongest possible message that our Olympics will not be contaminated by this exploitation.”

In January, two Church of England dioceses set down a motion for discussion at the General Synod, or clerical parliament, for a government crackdown on human trafficking in the run-up to the London 2012 Olympics, saying “anything like slavery is wrong”.

They pointed to the World Cup in Germany, where they said city officials adopted a “pragmatic” approach towards catering for the sexual desires of the estimated three million football fans who attended the tournament.

“Sex huts” or “sex garages” for prostitution were set up, filled with 40,000 extra prostitutes, while special licences were issued allowing prostitutes to offer sex on the street, they added.

About 500,000 sports fans a day are expected to roll into London for the two-week long Olympics.

Concerns have already been raised about the 2010 World Cup in South Africa.

While some studies suggested that prostitution levels may have in fact decreased during the World Cup in Germany, Jowell said: “I think this is a risk, it is a risk I am absolutely determined that London will mitigate, and that London will set an example for the world in future sporting events, basically outlawing trafficking, making it impossible for these young women, and young men, to be exploited in this way.”

“I think it is an issue that has to come out of the cupboard.”