"Everything was destroyed such that the programme couldn't be restarted at the time at all and never restarted," Jafar Dhia Jafar said of Iraq's nuclear plans on the BBC's Newsnight programme late on Wednesday.
Washington and London justified the Iraq war on the basis that Saddam at the very least had biological and chemical weapons and was prepared to use them.
No weapons of mass destruction have been found in Iraq more than a year after US President George W. Bush declared an end to major combat. British Prime Minister Tony Blair has said the weapons may never be found.
Jafar, called the father of Iraq's nuclear bomb programme, said Saddam could have used biological and chemical weapons in the 1991 Gulf War but chose not to.
"They were not available in 2003 because they had been destroyed and the programme was never reconstituted or reactivated, none of the programmes," he said.
It was unclear from where Jafar spoke to the programme.