The self-styled Islamic State (Isis) terror group should be "round the table" in future peace talks with Western governments, Owen Smith has suggested.
The Labour leadership challenger made the controversial comments after Jeremy Corbyn, who once called Hezbollah and Hamas "friends", ruled out negotiating with the militants, who have attempted to form a caliphate across Iraq and Syria.
But Smith, a former special adviser to New Labour Northern Ireland Secretary Paul Murphy, said: "Ultimately, all solutions to these crises, these sort 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. At the moment, Isil (Isis/Daesh) are clearly not interested in negotiating.
He added: "At some point, for us to resolve this, we will need to get people round the table."
The remarks came as Smith and Corbyn took party in a Labour leadership hustings on BBC News' Victoria Derbyshire LIVE programme. A pro-Corbyn source told IBTimes UK: "It shows how lightweight Owen is that he makes more gaffes than Frank Spencer."
Smith also claimed there was no split between Labour members and its parliamentary party, despite 172 Labour MPs backing a motion of 'no confidence' on Corbyn's leadership in June.
"I don't think there is a chasm between the PLP and the membership," Pontypridd MP. "Well, there's laughter there, but I think there has been a false narrative created that there has been a great big chasm."
Corbyn, meanwhile, urged Smith to re-join his shadow cabinet and defended his EU referendum campaign record. "Two thirds of all Labour supporters voted to Remain, less than one third of Conservative supporters voted to Remain," he said. "But there's also a message there in the referendum that the results were very different in different parts of the country – my constituency voted 70% to Remain, Owen's voted against Remain."
Smith replied: "They didn't actually, it was 50/50."
Corbyn, when challenger further on his performance by an audience member, added: "I did my best in that campaign."
UPDATE: 12:49 BST
A spokesperson for Smith said: "Owen is clear that there should be absolutely no negotiation with Daesh, or any terrorist group, until 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."