A super-casino in at the former Millennium Dome would bring with it huge crime, according to a campaign group.
The Dome would be home to the super-casino if Greenwich wins
A decision on the location for the super-casino will be made on Tuesday and Greenwich, in south-east London, is seen as one of the favourites.
Greenwich Chamber of Commerce has said the casino would regenerate the area.
But Chris Le Breton, of the South East London Against The Casino group, said: "Regeneration and gambling do not go."
The group fears a regional casino would increase levels of crime and create a new generation of young gamblers in the local community.
He added: "Greenwich has huge pockets of deprivation and it is those people that I am concerned about.
"Research from Canada, Australia, from all over the world suggests that for every £1 earned by the community £3 is spent clearing up the negative sides of crime and prostitution."
He said 75% of local people do not want a super casino.
AEG, the new owners of the Dome, says the Las Vegas-style casino is vital to its plans for the second stage of the redevelopment of the Dome.
It says £350m will be invested into the site which would include two hotels, a theatre, an exhibition centre, and an ice rink.
Ray Smith from The Greenwich Society, a charity which works for the improvement of the area, said the casino will help.
"There are parts of Greenwich that suffer high deprivation," he said. "Regeneration and job creation is very important."
Steve Nelson, from the Greenwich Chamber of Commerce, said: "We need the super casino not for the casino itself but for what it brings with it.
"We're building for the future. When the Olympics arrive people will want to stay there.
"If we have the super-casino in London people are going to flock to Greenwich from all over the world."