CHALK RIVER, Ont. - Federal Health Minister Tony Clement is dismissing criticism of the Conservative government's handling of the medical isotope crisis, insisting that he and his colleagues acted swiftly.

Clement says he and Natural Resources Minister Gary Lunn moved as quickly as possible after they learned that the 50-year-old Chalk River nuclear reactor had been shut down for safety violations.

The reactor produces most of the world's nuclear isotopes for medical treatment and its closure - after months of warnings from the country's nuclear safety agency - created a worldwide shortage.

Clement suggested someone other than he and Lunn were to blame for the crisis and he vowed to thoroughly investigate what happened.

The reactor is set to restart this week after Parliament passed legislation over-riding the safety closure order.

Clement moved to limit fallout from controversy by taking reporters on a tour of the reactor today.

The move came as the Conservative-appointed former chairman of Atomic Energy of Canada Ltd. lashed out the Tory government's handling of his resignation, calling it "a clumsy piece of political opportunism."