Labour leadership contender Owen Smith has been accused of being unfit for high office after he suggested Islamic State (IS) would have to be brought into peace talks to end the Syrian civil war.

In the latest leadership debate, Mr Smith said that "all of the actors" involved in the conflict would have to be brought into the negotiations if there was to be a successful conclusion to the conflict.

His comments sparked an outcry, with one Conservative member of the Commons Defence Committee - former Army officer Johnny Mercer - saying they showed his "unfitness for leadership".

Read more: Leadership hopeful Owen Smith says Scottish Labour party did not grasp national pride and identity

A spokesman for Jeremy Corbyn said the remarks were "hasty and ill-considered".

In contrast to Mr Smith, the Labour leader insisted that there could be no place for the terror group - also referred to as Isil, Isis or Daesh - at the negotiating table.

Asked by presenter Victoria Derbyshire in the BBC televised debate whether IS should be included in peace talks, Mr Smith referred to his time as a special adviser to Northern Ireland secretary Paul (now Lord) Murphy to argue that all parties to the conflict should be involved.

"Ultimately all solutions to these sorts of international crises do come about through dialogue so eventually, if we are to try and solve this, all of the actors do need to be involved.

"But at the moment Isil are clearly not interested in negotiating," he said.

Asked the same question, Mr Corbyn said: "They are not going to be round the table. No."

Mr Mercer said: "Owen Smith's suggestion that we should get Isis 'round the table' demonstrates his unfitness for leadership.

"Everyone knows negotiation is far more desirable than violence in any conflict, but to suggest it in this case is to entirely misunderstand and fail to grasp the challenge posed by Daesh.

Read more: Leadership hopeful Owen Smith says Scottish Labour party did not grasp national pride and identity

"His desperate attempts to out-Corbyn Jeremy Corbyn have led him to the view that barbaric murderers who behead journalists and lynch homosexuals are now the sort of people that we should negotiate with."

A spokesman for Mr Smith later made clear that he believed there could be no negotiation with IS unless they "renounce violence, cease all acts of terror and commit themselves to a peaceful settlement".

"Owen's experience of helping to bring about peace in Northern Ireland is that eventually all parties who truly believe in delivering peace have to be around the table.

"In the Middle East at the moment that clearly doesn't include - and may never include - Daesh," the spokesman said.

Much of the debate was dominated by accusations that Mr Corbyn had failed to crack down on anti-Semitic and misogynistic abuse within the party.

One young Labour supporter in the studio audience said she would "feel more comfortable" going to a Conservative Party conference and saying she was a Labour supporter than going to a Labour conference and saying she supported Mr Smith.

Read more: Leadership hopeful Owen Smith says Scottish Labour party did not grasp national pride and identity

Mr Corbyn insisted he had repeatedly made clear that abuse had no place in the party and that the rules were being tightened to deal with the issue.

"I have dealt with very strongly and very robustly any complaints about abuse. It has no place in any political party. I have made absolutely clear that any kind of abuse is totally unacceptable in any form," he said.

However Mr Smith said they should be "deeply ashamed" that the party was mired in controversy about its attitude towards women and Jewish people and added that Mr Corbyn had "just not seemed bothered enough by it".

"Lots of my female MP colleagues feel Jeremy wasn't supportive enough. Lots of the Jewish MP colleagues feel Jeremy wasn't quick enough to condemn anti-Semitic abuse," he said.

"We are the Labour Party and we are having a debate on national television about anti-Semitism and misogyny within the Labour Party and that should make us all deeply ashamed."

At the end of the debate, the majority of undecideds among the audience - which was made up of Labour members, supporters and potential supporters - indicated they would back Mr Corbyn for the leadership.