Britain's Olympic bosses have been grilled over a major sponsorship deal with McDonald's.

The London Green Party said the deal flouted a bid promise to use "local, seasonal and organic" food at the London 2012 Games.

The International Olympic Committee (IOC) - not the London team - has chosen McDonald's as one of its 12 long-term partners.

"While I appreciate that the London organizers are bound by the IOC's sponsorship deal, I really do feel this is a big let down," said London Assembly Greens leader Jenny Jones.

"The games are a showcase. People attending should be inspired to lead healthier lives, not sit there shovelling down junk-food."

In the bid document "Towards a one planet Olympics", organisers promised to support "consumption of local, seasonal and organic produce, with reduced amount of animal protein and packaging".

Yesterday the London Assembly questioned Paul Deighton, chief executive of the London Organising Committee of the Olympic Games (Logoc), about the deal.

The agreement allowed McDonald's "to be suppliers of their particular food area so we won't see alternative burger suppliers", he said. "But they don't have control over all our food supply."

London has to raise about £2 billion in sponsorships, of which about £530 million will come from the 12 IOC partners. Apart from McDonald's, they include Coca-Cola, Visa, Panasonic and Samsung.

Deighton said his team would announce the first of its own six sponsors by next March.

100,000 volunteers

Meanwhile, a teenage brother and sister from north-west London have become the 100,000th to sign up as volunteers at 2012.

"We are so excited that the Olympic Games and Paralympic Games are coming to London," said Yousef (18) and Leila Ziu (15), of Cricklewood. "We want to be part of it."

Only 70,000 volunteers will be chosen from the applicants, based on their skills and volunteering experience.

At the Games, they will help with anything from transport and security to First Aid and translation.

"Volunteers are the lifeblood of the Olympic Games and Paralympic Games," said Lord Sebastian Coe, the Logoc chairman. "I urge anyone who wants to be part of the best Games ever to step forward."