The fixing of contests is now more of a threat to the Olympic Games than doping, Hugh Robertson, the minister for sport, has warned amid security preparations to counter the threat of attempts to bribe athletes and players at London 2012.

"You cannot underestimate the threat this poses because the moment that spectators start to feel that what they are seeing in front of them is not a true contest, that is when spectators stop turning up and the whole thing falls to pieces," Robertson said.

The minister told the Sunday Times that he believes game-fixing now posed the biggest threat to the reputation of the Olympic Games. "At some stage over the next two or three years, we will have some other sort of betting scandal in some sport. I just hope it is not at the Olympics," Robertson said.

Huge amounts of money are expected to be bet as gambling syndicates – particularly on the Indian subcontinent and in the Far East – focus on events in London this summer. The betting exchange Betfair says that up to £300m could be wagered in Britain alone.

Robertson said that betting authorities in the West were "well set up" to spot illegal activities but criticised the lack of regulation on the subcontinent and in the Far East. "If you look at the most recent high-profile incident – the Pakistani cricketers [caught spot-fixing] at Lord's – the issue is not of betting syndicates in this part of the world. It is in illegal betting syndicates on the Indian subcontinent and elsewhere, where huge sums of money change hands."

The minister drew particular attention to spot-betting as the major danger. In spot-betting, syndicates wager tens of thousands of pounds on individual incidents within matches, such as the number of short corners in hockey.

A dedicated intelligence unit will operate at London 2012 in an attempt to discover irregular betting patterns and any attempts to bribe participants. Athletes will be warned about the possibility of approaches by fixers.