An economist says hosting the Olympic Games is a bad idea for almost all cities.

Brazil has been under financial strain to get the infrastructure ready to host the games in Rio.

Professor Andrew Zimbalist is the author of the book Circus Maximus that examines the economic gamble of hosting the games.

He told Mike Hosking host countries end up spending far more than what they get in return.

"In return for the $15-20 billion investment, they get about $4-4.5 billion back in revenue. That's not a very good financial balance."

He said the IOC's argument that it will lead to increased tourism, trade and investment does not stack up.

"The empirical studies of the impact of hosting the Olympics suggests that those purported long term gains are illusory - they don't happen. And I think we can see that time and time again in recent Olympic history."