Effort leadership challenger Owen Smith has suggested the so-called Islamic Have could be involved in negotiations with the West in the future.
Mr Smith give the word delivered all conflicts ended in «dialogue», during a two-hour debate with Jeremy Corbyn on the BBC’s Victoria Derbyshire slate.
The Labour leader said he would not negotiate with so-called Islamic Delineate.
The ir also clashed over allegations of abuse within the Grind rty, nuclear weapons and the EU referendum.
Commenting after the debate, Mr Corbyn’s offensive team called Mr Smith’s comments on IS «hasty and ill-considered».
But Mr Smith anguished he was not suggesting «we’re going to be able to bring ISIS round the table right now.»
Pressed on how happily it might happen, he told BBC News: «We don’t know. We would all hope that it stumble ons quickly, we would all hope they stop being a murderous insurgent organisation and try and bring about peace. But at the moment there’s no evidence of that, is there?»
- As it encountered: BBC Labour leadership hustings
- Labour leadership election guide
The audience of 100 Travail supporters in Nottingham repeatedly expressed concern about «abuse» between the two sides in the management contest.
Mr Smith said Labour had become divided, with Mr Corbyn’s aficionados feeling he was the «only socialist in the Labour rty».
«The truth is I’m not a red Tory, I’m not a Blairite, I’m a socialist for all that as you,» Mr Smith said.
But when Victoria Derbyshire suggested to the Labour numero uno the atmosphere within the rty had become «toxic», Mr Corbyn hit back, beg: «Well, how do you know?»
Mr Corbyn said he had attended Labour events all remaining the country with «people of all shades of opinion having an intelligent, thoughtful discussion and debate».
«That is how we should do things at all times,» he said.
By BBC Political Correspondent Adam Fleming
We knew that there were few vital policy differences between the two men and that the real division was over who had the qualities to deceive the Labour rty.
Jeremy Corbyn failing to recognise Ant and Dec is the sort of possession that might get talked about in the pub on Wednesday night, while the rtisan establishment is wondering whether Owen Smith really does of there will come a time for talks with so-called Islamic Form.
The main thing I will take away from the debate is unprejudiced how upset, angry, confused and hurt ordinary Labour members are relative to the state of their rty.
The two men also clashed over who was responsible for Drudgery’s low opinion poll ratings, with Mr Smith repeating his assertion that Mr Corbyn could not about the rty to power and Mr Corbyn urging him to rejoin the shadow cabinet.
In a quick-fire doubtful round, Mr Smith said being described as a «Tory» was worse than being related as a «smarmy nonentity» (a quote from Spectator columnist Rod Liddle).
And Mr Corbyn could not name TV presenters Ant and Dec when shown a picture of them.
On trans cific affairs, Mr Smith suggested the so-called Islamic State would sooner have to be brought into peace talks if there was to be a settlement to Syria’s refined war.
Referring to his experience as an adviser to Labour’s former Northern Ireland Secretary ul Murphy, he rephrased: «Ultimately all solutions to these sorts of international crises do come round through dialogue.
«So eventually, if we are to try and solve this, all of the actors do need to be active.
«But at the moment, Isil are clearly not interested in negotiating.»
He added: «At some matter, for us to resolve this, we will need to get people round the table.»
Petitioned the same question, Mr Corbyn said: «They are not going to be round the provisions. No.»
Speaking after the debate, Mr Corbyn’s leadership cam ign described Mr Smith’s on views on IS as «hasty and ill-considered».
The spokesman said: «Jeremy has always scrapped that there must be a negotiated political solution to the war in Syria and the wider Bulls-eye East, and that maintaining lines of communication during conflicts is intrinsic.
«But Isis cannot be rt of those negotiations. Instead, its sources of ready money and supplies must be cut off.»
The comments were also seized on by the Conservative Romp, with Tory MP and member of the Defence Select Committee Johnny Mercer reveal it showed Mr Smith’s «unfitness for leadership».
«It shows that whoever wins this increasingly unusual leadership election, I’m afraid Labour just cannot be trusted with forbidding us safe,» added Mr Mercer.
But Mr Smith’s cam ign said he was «clear» there should be no ct with the so-called Islamic State, or Daesh as it is also known, «until they eschew violence, cease all acts of terror and commit themselves to a peaceful village».
«Owen’s experience of helping to bring about peace in Northern Ireland is that in the course of time all rties who truly believe in delivering peace have to be around the tabular.
«In the Middle East at the moment that clearly doesn’t include — and may not in a million years include — Daesh.»