Jeremy Corbyn is on track for a dramatic showdown with his own shadow cabinet after insisting that he alone has the final decision on whether Labour opposes airstrikes in Syria.
The leader also insisted MPs must listen to the "voice" of the party membership, who overwhelmingly elected him, as he delivered an impassioned critique of David Cameron's case for attacking Islamic State in its heartlands.
The intervention, in an interview on the BBC's Andrew Marr show, is likely to inflame tensions further between Mr Corbyn and his top team - a majority of whom are believed to support airstrikes. The shadow cabinet is due to meet tomorrow ahead of a potentially explosive gathering of the Parliamentary Party in the evening.
Mr Corbyn dismissed intelligence advice that IS was using its territory in Syria to prepare terror atrocities against Britain, arguing that "those attacks could be planned anywhere".
He also "seriously questioned" the Prime Minister's claim that there are 70,000 moderate Syrian troops to tackle IS forces on the ground, and voiced doubts about their "loyalties".
Mr Corbyn said a unanimously-passed UN Security Council resolution calling for "all necessary measures" against the terrorist groups did not provide justification for military action.
Bombing IS targets in Syria would be a "distraction from the political process" to end the civil war, and would lead to civilian casualties, he insisted.
Asked whether Labour MPs - around half of whom are thought to support action - would be given a free vote, Mr Corbyn said: "No decision has been made on that yet, I am going to find out what MPs think.
"Obviously there are strong views on both directions. We will have a further discussion on this. We will make that decision not at this moment but later on."
Mr Corbyn said he had received 70,000 responses to a survey sent out to Labour supporters on Friday canvassing their opinions, and a decision would be taken "as a party". The survey has been criticised as an attempt to use his grassroots powerbase to "bounce" the shadow cabinet into submitting.
"My view about the membership of the Labour Party, they must have a voice," he said.
"Labour MPs need to listen to that voice, they need to try and understand where people are coming from on this. We will come to a decision as a party."
The veteran left-winger, who has been a serial rebel through his Commons career, said: "I understand dissent, I understand disagreement from leadership."
But asked if the whipping position would be a collective decision by the shadow cabinet, Mr Corbyn said: "It is the leader who decides. I will make up my mind in due course."