Johnson claimed he was concerned about current plans to leave a third of the Stadium's seats uncovered.

 

Johnson was asked about the Stadium during a climate change summit in South Korea, where he also visited facilities used when Seoul hosted the 1988 Olympics.

 

He said: "I have yet to see a very convincing explanation of what happens if it rains heavily on the night of the opening ceremony.

 

Asked if he would insist on roofing, Johnson said: "It is a discussion that is going on."

 

But a spokesman for the Olympic Delivery Authority appeared to signal that there was no chance of any changes being undertaken.

 

He said: "The design for the stadium, including its roof, was agreed in 2007.

 

"The roof will cover around two-thirds of spectators, in line with Olympic stadiums of the recent past."

 

 

At the same conference Johnson outlined plans to make London "the cleanest, greenest city on earth" by the 2012 Olympics and called for commitments from other world cities.

 

Leaders of the world's 40 largest cities, plus 17 affiliate municipalities, are meeting in Seoul this week for a summit on combating global warming - the third to be held since 2005.
 

Johnson said: "What we should do in Seoul is agree that we will stop the endless addiction of mankind to the internal combustion engine."

He claimed that the world's cities consume 75 per cent of its energy and produce 80 per cent of the emissions which cause climate change.

Johnson said: "The problem of our planet is an urban problem.

 

"I don't want to walk away with a communique which contains nothing but warm words and hot air... it's important we agree some specific measures."
 

He said the capital wants to use the Olympics "to drive the greening and the improvement of our city" and noted that London is committed to reduce carbon emissions by 60 per cent by 2025.
 

Johnson said the key measure was addressing the problems relating to domestic and commercial buildings, which accounted for 70 percent of carbon dioxide emissions in London.
 

This involved retrofitting - installing lagging - in large numbers of public buildings.

Johnson proclaimed himself a "passionate cyclist" and said he would push ahead with cycle super-highways around London.
 

He also called for "real progress" by cities worldwide towards the electrification of municipal fleets and other vehicles.

 

Johnson said: "That's one of the things we are hoping to achieve in Seoul."
 

London's air quality problem, he said, was caused by vehicle emissions from 8,300 antiquated diesel buses which could be replaced by low-carbon vehicles.
 

There were also 32,000 taxis running on diesel fuel which could be replaced by electric vehicles.
 

Johnson said there would be a substantial programme in the next few years to produce a "cleaner, greener" bus for his city.