Tony Blair appeared to suggest today that military action might be necessary to stop Iran developing its weapons programmes.
The former prime minister, who is now a Middle East peace envoy, said Tehran's actions have made him even more afraid today that a rogue state could supply weapons of mass destruction to terrorists than he was when he took Britain to war with Iraq in 2003.
He warned that world leaders now face the same kinds of decision about the dangers posed by repressive regimes as he did seven years ago.
"My judgment - and it may be other people don't take this view, and that's for the leaders of today to make their judgment - is we don't take any risks with this issue," he said.
Giving evidence to the Chilcot Inquiry into the Iraq war, Mr Blair raised serious concerns about Tehran's links with terrorist organisations.
He said: "My fear was - and I would say I hold this fear stronger today than I did back then as a result of what Iran particularly today is doing - my fear is that states that are highly repressive or failed, the danger of a WMD link is that they become porous, they construct all sorts of different alliances with people."
He added: "I spend a lot of time obviously out in the region today.
"When I look at the way that Iran today links up with terror groups - and this is a different topic for a different day - but I would say that a large part of the destabilisation in the Middle East at the present time comes from Iran."
Mr Blair became the Middle East envoy for the Quartet of the US, Russia, the UN and the EU after leaving Downing Street in 2007.