Cherie Blair is to become an ambassador for the London 2012 Olympic bid.

The prime minister's wife made the announcement in Athens where she had been watching British athletes compete.

She said: "I am delighted to be invited to join the team of ambassadors for the London 2012 bid team.

"I have always been a great supporter of the plan to bring the Olympic Games to London in 2012 and look forward to helping that aim become a reality."

The appointment will help convince the International Olympic Committee that the bid has the full backing of the government.

London's attempt to get the games has had several recent setbacks, including the departure of Barbara Cassani, the American businesswoman who was leading it.

Mrs Blair has already travelled to Athens once with her husband for the opening day of the Games, where they were both photographed wearing Team GB T-shirts.

The final decision over who will host the 2012 Games will be announced in Singapore next July. Paris, New York, Madrid and Moscow are also in contention.

A Downing Street spokesman said: "Mrs Blair is very pleased to have received the invitation to be an ambassador.

"She has been very supportive of the London bid and her visit to Athens over the weekend is a fact-finding mission to see the work involved behind the scenes and also to give her support to Team GB."