MOLE Valley should be prepared for up to 500,000 spectators during the Olympic cycling races in July, councillors have warned.
A council report setting out plans for a "big weekend" of events estimates 90,000 people per day will watch the races in the district on July 28 and 29.
But some Mole Valley District Council members believe the real number could be closer to 250,000 on both the Saturday and Sunday.
Speaking at a scrutiny committee meeting, Councillor Chris Townsend (Ind, Ashtead Park) said: "We are talking about a once-in-a-lifetime opportunity here and I think it is very important that we do have such a weekend. It's a cracking idea.
"But I think the 90,000 is a minimum number. I think it's quite possible that we could get a quarter of a million."
Councillor Emile Aboud (Con, Fetcham West) said: "We have got to look very, very carefully at whether we can accommodate more than 90,000 people.
"Where on earth we are going to find space for 250,000 people I have no idea, but we have got to try."
But council leader James Friend said his colleagues were "pulling numbers out of the air". "90,000 is a reasonable number to plan for," he said. "I would be surprised if it goes above that.
"We are quite a big part of the route, people will squash around a bit further and will be two or three deep in places."
The men's and women's Olympic cycle races will pass through Mole Valley on the first weekend of the games, visiting locations including Dorking, Leatherhead and Box Hill.
Street parties, fairground rides, musical performances and art exhibitions are planned, while big screens will be placed in Dorking and Leatherhead town centres.
John Meudell, of Mole Valley Cycle Forum, believes the council should also plan for the days before and after the races.
He said: "I am concerned that the people involved with the Olympics are only looking at the two days, Saturday and Sunday, when in practice they should look at it as at least five days and possibly a week.
"We are so near the continent, Europe is the heart of cycle racing, so people will rent camper vans. If the district wants to make something of it they have got to do the research to find out exactly how many people are looking to come, and figure out how to provide for them."