The Labour leader restarted his party’s campaign after a pause following the atrocity with a speech linking UK foreign policy in Afghanistan, Iraq and Libya to the threat from terrorism.
Mr Corbyn reiterated his belief that the so-called “War on Terror” had failed, and pledged he would only send British troops into harm’s way if they could “secure an outcome that delivers lasting peace”.
He was rounded on by opponents who suggested Mr Corbyn was politicising a tragedy and blaming the UK for terrorist attacks on its soil.
Acknowledging that his comments would be controversial, the Labour leader called on critics to raise the tone of debate following the tragedy in Manchester, and warned them not to question his patriotism.
And, in a BBC interview with Andrew Neil last night, Mr Corbyn said airstrikes in support of Libyan rebels in 2011 had created a “huge ungoverned space” that was the source of the “awful extremism” behind Monday’s attack.
He said: “If we are to have a secure future, we’ve got to look at ungoverned spaces around the world and the consequences of our wars of intervention. This is not just me; as I said it’s MI5, it’s the foreign affairs select committee, it’s a number of other people.”
The comments drew an angry reaction from Conservative figures, led by Prime Minister Theresa May and armed forces minister Ben Wallace, who condemned them as “crassly timed”.
Mrs May, who yesterday attended a summit of the Group of Seven countries in Sicily, slammed Mr Corbyn’s position when she was asked about it at a news conference.
Mrs May said that, while she was at the summit rallying support for the fight against terrorism, “Jeremy Corbyn has said that terror attacks in Britain are our own fault, and he has said that just a few days after one of the worst terror attacks” in the country’s history.
“There can never, ever, be an excuse for terrorism,” she said, adding that “the choice people face at the general election has become starker”.
Some observers have interpreted Mr Corbyn’s speech as a bid to win back the many Labour supporters who turned away from the party in the aftermath of then prime minister Tony Blair’s decision to join the US-led invasion of Iraq in 2003.
Home Secretary Amber Rudd said it was “outrageous to suggest that there is any link, any justification, for the events that took place in Manchester with the UK’s foreign policy”, while Defence Secretary Michael Fallon claimed Mr Corbyn was “too quick to make excuses for the actions of our enemies and too willing to oppose the measures and people that keep us safe”.
Mr Corbyn said the UK had to be “honest about what threatens our security”.
He said: “Those causes certainly cannot be reduced to foreign policy decisions alone. Over the past 15 years or so, a sub-culture of often suicidal violence has developed among a tiny minority of mainly young men, falsely drawing authority from Islamic beliefs and often nurtured in a prison system in urgent need of resources and reform.
“And no rationale based on the actions of any government can remotely excuse, or even adequately explain, outrages like this week’s massacre.
“But we must be brave enough to admit the War on Terror is simply not working.”
He also pledged to reverse cuts to the police, saying: “We cannot be protected and cared for on the cheap.”
He said: “There can be no love of country if there is neglect or disregard for its people. No government can prevent every terrorist attack.”
But Mr Corbyn added that it was the government’s responsibility to “minimise that chance” by giving the police sufficient resource and ensuring that foreign policy “reduces rather than increases the threat to this country”.
Liberal Democrat leader Tim Farron yesterday joined criticism of the speech’s timing, in the same week as the Manchester bombing, accusing Mr Corbyn of trying to “use that grotesque act to make a political point”.
But an attack on Mr Corbyn’s message appeared to backfire on Mr Farron after comments from 2015 surfaced in which Mr Farron called the war in Iraq “counterproductive and illegal”, and said the rise of the Islamic State terrorist group had been “a consequence” of the UK’s intervention.
Foreign Secretary Boris Johnson said that rather than trying to understand their motivations, the country should be “uniting to defeat these people”. He said: “They are wrong, their view of the world is a corruption and perversion of Islam and it can be completely confounded.
“But now is not the time to do anything to subtract from the fundamental responsibility of those individuals, that individual in particular, who committed this atrocity and I think it is absolutely monstrous that anybody should seek to do so.”
However, in a column for the Spectator magazine a week after the 7 July, 2005 bombing in London, Mr Johnson argued that the war in Iraq “did not create the problem of murderous Islamic fundamentalists” but had “unquestionably sharpened the resentments felt by such people in this country”.
Referring to violent extremism as a “poison”, Mr Johnson wrote: “The Iraq War did not introduce the poison into our bloodstream but, yes, the war did help to potentiate that poison.”
The sister of the Manchester bomber has claimed that Salman Abedi had launched his attack seeking “revenge” for civilian deaths during western military interventions in the Middle East.
Mr Corbyn also claimed during his BBC interview that he “never met the IRA” and never supported violent republicanism.
Mr Corbyn also said he thought the Nato alliance should have been wound up at the end of the Cold War, and cast new doubt on Labour’s Trident policy.
“I didn’t support the IRA. I don’t support the IRA,” Mr Corbyn said. “What I want everywhere is a peace process.” Asked why he invited convicted IRA terrorists to Westminster shortly after the Brighton bombing, Mr Corbyn said: “I always wanted and always do want peace, always want a dialogue between people of vastly different backgrounds.”
Mr Corbyn again threw Labour’s policy on nuclear weapons into disarray despite the party’s manifesto commitment to renew the UK’s submarine-based deterrent.
The Labour leader said a defence review if his party forms the next government would “look at the role of nuclear weapons as it will look at everything”, contradicting previous clarifications by party spokespeople.