The Olympic Stadium is taking shape in east London
The shadow minister for the 2012 London Olympics has said he would make the stadium into a football venue after the Games, if his party was in power.
Hugh Robertson rejects the government's stance that the stadium must be scaled down from 80,000 seats to 25,000 seats.
London Mayor Boris Johnson has said the east London venue could help England's bid to host the 2018 World Cup.
Mr Robertson said using it as a football venue would be the best way of making the stadium profitable.
After the Games, the plan is for the venue, in Stratford, east London, to host athletics meetings as well as housing a secondary school, a sports academy and the English Institute of Sport.
Mr Robertson said: "We have to make that stadium commercially viable in post Olympics mode.
"The one way that I can see of making it commercially viable - because there will not be a huge pot of public money to keep the thing going - the one way I can see of making it commercially viable post 2012 is to incorporate another sports use.
"I think it's most likely to be football - alongside the world class athletics use that we must guarantee because it was part of our bid."
In July Olympics Mnister Tessa Jowell said: "We don't need another football stadium - we've got Wembley.
"Funding the maintenance of a stadium between 2012 and 2018 is quite a stretch, so I think we will continue to develop the plan that we have for the Olympic stadium," added Jowell.
"We made a very clear commitment in the bid book that the Olympic stadium in legacy will be a 20-25,000-seater athletic stadium with the provision for a warm-up track so that London and indeed the UK will have a grand prix athletics stadium."