International Olympic Committee vice-president John Coates on Tuesday piled pressure on 2016 host Rio de Janeiro, blasting its preparations as the worst he has ever seen.

The Australian, who has made six visits to Rio as a member of the IOC Coordination Commission overseeing the Games, painted a dire picture of the progress being made, which he said was of "critical concern".

He told an Olympic Forum in Sydney that the IOC had been forced to take "unprecedented" action, embedding experts in Rio’s Organizing Committee to ensure the sporting spectacle proceeds.

"The IOC has formed a special task force to try and speed up preparations but the situation is critical on the ground," he said, adding it was "the worst I have experienced".

"The IOC has adopted a more hands-on role, it is unprecedented for the IOC but there is no Plan B. We are going to Rio."

With the clock rapidly ticking before the first Olympics in South America, many facilities in Rio have yet to be completed because of construction delays and soaring costs.

Earlier this month the IOC drew up a list of urgent recommendations aimed at breathing life into the flagging preparations.

These include the creation of three task forces with a number of aims including easing the fears of an increasingly angry population who have protested at the costs of both the Olympics and the 2014 World Cup, which is also in Brazil.

Furthermore, international sports federations will send teams of experts to work alongside local organizers in a model of co-operation which was used in the build-up to the Sochi Winter Olympics.

"I think this is a worse situation than Athens (in 2004)," said Coates, who has been involved in the Olympics for nearly 40 years.

"In Athens, we were dealing with one government and some city responsibilities. Here, there's three.

"There is little co-ordination between the federal, the state government and the city -- which is responsible for a lot of the construction," he added.

"And this is against a city that's got social issues that also have to be addressed; a country that's also trying to deal with the FIFA World Cup coming up in a few months.

"It's the worst that I've experienced."