Jack Lemley, who resigned as chairman of the Olympic Delivery Authority (ODA) last month, angrily rejected claims by Ken Livingstone, the Mayor of London, that he left after having had major heart surgery. The American engineer said yesterday that he was training three times a week, planning a skiing trip and had a schedule that “would kill a horse”.

Mr Lemley, 71, insisted that his health was not connected to his resignation but he was “very, very concerned” about the extent of toxic material and hazardous waste on the 757-acre site, much of which was industrial land. The clean-up operation could also unearth unexploded bombs dropped during the Blitz.

The American engineer was increasingly frustrated that the process of cleaning the land — known as remediation — had not begun, although contractors had been appointed to carry out the task in June.

They have carried out preparatory work, digging boreholes to examine soil samples, but will not begin full-scale remediation until next year. The ODA has yet to take possession of the entire Olympic site.

Mr Lemley believes that the land is heavily polluted and that the clean-up could delay construction and send the costs — already expected to reach £6 billion — out of control.

Tessa Jowell, the Culture Secretary, appointed Mr Lemley and will be questioned about his abrupt resignation and the rising budget when she appears before a Commons select committee next week.

A spokeswoman for Mr Lemley said: “He was deeply concerned about the budget — he has seen the consultants’ reports — and lack of progress, particularly regarding remediation of the site. He strongly believes that there is not enough knowledge of the contamination and potential hazards buried there and what it will take to remediate it.”

She added that Mr Lemley, who has returned to his company in Boise, Idaho, believed that the clean-up was an important issue that was not being addressed.

He was also clearly enraged by the intervention of Mr Livingstone, who told the London Assembly that he had had “major heart surgery”. Mr Livingstone said that Mr Lemley had lacked “vibrancy” after returning to work in July.

Mr Lemley’s office robustly denied the claims and said that he was in very good health. His spokeswoman told The Times in an e-mail: “Jack Lemley did not have major surgery. He was treated for arrhythmia, spent some time with family, then returned to England to work. I ask you, how is Mr Livingstone qualified to diagnose anyone’s condition by ‘noticing’ them? If people are judged at work by their appearance, there wouldn’t be many people working, would there?” Sir Roy McNulty, the acting chairman of the ODA, has conceded that there were serious differences between Mr Lemley and senior staff, especially over how much work had been carried out on site. But David Higgins, the ODA’s chief executive, has said he is confident that the land “is not a highly contaminated site”.

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