It would be a "very dangerous experiment" for the UK to give Labour leader Jeremy Corbyn power, Tony Blair has told the BBC's This Week's World.
The former Labour prime minister said the centre ground needed to work out how to recover and get "its mojo back".
He also said he had "real humility" about the decisions he took on Iraq.
But shadow chancellor John McDonnell said Mr Blair's comments were "a bit rich", adding: "I look forward to the Chilcot report."
During the interview Mr Blair said the dislike many felt for him was less to do with the Iraq War and more to do with him winning three general elections for Labour.
"There are people who disagree with me for reasons that they say are to do with, say, Iraq, but actually are to do with the fact I won three elections for the Labour Party and they didn't like it," he said.
'Populist policy making'
Mr Blair has been a vocal critic of Mr Corbyn in the past, warning before the left-wing MP's leadership election victory that the party risked "annihilation" if he won.
In an interview with the BBC's This Week's World, Mr Blair - Labour leader from 1994 to 2007, and PM for 10 of those years - dismissed the idea that Mr Corbyn's election as party leader was a direct rejection of him and his policies.
"No," he said, "I think it's a result of the way the world works these days. But it's a big challenge for the centre... It would be a very dangerous experiment for a major western country to get gripped by this type of populist policy-making, left or right."
He added: "I do think the centre ground needs to work out how it recovers... gets its mojo back and gets the initiative back in the political debate, because... these guys aren't providing answers, not on the economy, not on foreign policy."
John McDonnell, shadow chancellor and close ally of Mr Corbyn dismissed Mr Blair's comments.
"I find that a bit rich from a prime minister who took us into the Iraq war which resulted in half a million deaths. So I think it's inappropriate for him to comment and I look forward to the Chilcot report," he said.
'A generation fight'
Sir John Chilcot's long-awaited report into how UK forces came to participate in the US-led invasion of Iraq in 2003 and its aftermath, is to be published on 6 July.
Ahead of its publication, Mr Blair told This Week's World: "I have a real humility about the decisions that I took and the issues around them.
"I was trying to deal with this in the aftermath of 9/11 and it was very tough - it was very difficult."
The former PM, who set up a foundation which works to promote greater understanding between the world's religions and to challenge extremism and prejudice, said the West was not to blame for the situation in the Middle East.
And he warned of bigger terrorist attacks on Europe in future.
"You've got to open your eyes to the problem. If we don't do that we're going to store up an even bigger problem for ourselves, and we face the problem in Europe, I'm afraid, of even bigger terror attacks.
"I think we need to be in no doubt at all about the people we're dealing with here. If they could kill larger numbers of people that's what they would do," he said.
The threat, he said, was "different... from anything we have faced before" and he said it required a "different type of policy response and... a different rhythm of thinking", as it would be a "generation fight, it's not a fight that's going to be resolved in one year, two years, or even 10".
Mr Blair also called for action to redress the widespread problem of indoctrination of Muslim children in extremist ideologies across the Middle East.
He said there needed to be a global commitment, where countries promoted cultural tolerance and rooted out cultural prejudice within their education systems.
"If you end up polluting the mind of your people as they're growing up within your country, in today's world where the boundaries come down where there is much more migration and integration, then that is not just for your country - it's a problem for all of us."