The former chairman of the Olympic Delivery Authority says Games costs will exceed government's £2.4bn estimate

Jack Lemely, the former chairman of the Olympic Delivery Authority, has warned that the 2012 Games in London will cost far more than the £2.4bn originally stated by the government.

Lemley said: “The costs are going to go up on an exponential basis, and I’m just not going top be a part of it.”

Lemley quit the ODA two weeks ago, after less than a year in the job, and returned to America. Frustrated about lack of progress, he said: "I went there to build things, not to sit and talk about it. So I felt it best to leave the post and come home."

His comments were made during an interview with his local paper, the Idaho Statesman, published on Tuesday. Causing further embarrassment to the ODA, more details of that interview were revealed in today’s Evening Standard newspaper, with Lemley warning that costs would spiral out of control.

He said: “I’ve never walked away from a project, ever, until I retired from the London 2012 programme and it was so political that I think there is going to be a huge difficulty in the completion, both in terms of time and money. And it’s much more difficult because there is so much time being lost now.

“I think at the end of the day, if I’m wrong and they can do it all in their budget, then maybe I’ll have some regrets about it…but if the team can’t do it, I don’t want my reputation ruined. So I felt it was better to come home now than face it in five or six years.”

His publicist, Perri Capell, told Building: “Jack did not expect his Idaho statesman interview to be so widely disseminated and it's likely that any more comments won't be helpful to the Olympics.”