Weapons of mass destruction do not exist in Iraq and it is "delusional" to think they will be found, says former chief US weapons inspector David Kay.
Kay has repeatedly said there are no WMDs in Iraq
Mr Kay told BBC Radio 4's Today programme that British and American leaders should simply apologise and admit that they were wrong.
He said Saddam Hussein had intended to reconstitute his weapons programme at some point and had acted illegally.
However, there were no actual WMD stockpiles, he said.
Mr Kay led the hunt for weapons of mass destruction in Iraq until he stepped down as head of the Iraq Survey Group in January.
He said at the time that he did not believe there had been large-scale production of chemical or biological weapons in Iraq since the end of the first Gulf War in 1991.
In his latest comments, Mr Kay referred to the UK Prime Minister, Tony Blair, by name.
"Anyone out there holding - as I gather Prime Minister Blair has recently said - the prospect that, in fact, the Iraq Survey Group is going to unmask actual weapons of mass destruction, are really delusional," he said.
"There is nothing there. There is a programme there. There was an intention of Saddam Hussein at some point to reconstitute it.
"There were clearly illegal activities, clear violations of UN Security Council resolutions. We have accumulated that evidence and really have accumulated that evidence to a considerable degree four months ago.
"There are not actual stockpiles of newly produced weapons of mass destruction."
Mr Kay repeated his previous assertions that the US-led coalition had been mistaken in its assumption that Saddam Hussein had possessed the banned weapons.
"We simply got it wrong," he said. "Iraq was a dangerous country, Saddam was an evil man and we are better off
without him and all of that. But we were wrong in our estimation."