Labour leader says decision to join attack against regime should not be made by cabinet alone.

Jeremy Corbyn has demanded a private briefing on the government’s intelligence about the Douma chemical weapons attack, saying “more bombing, more killing, more war will not save life” in Syria.

Repeating his declaration that parliament must be consulted before military action is taken, the Labour leader urged Theresa May to learn lessons from the Chilcot report showing failures in the lead-up to the Iraq war.

As cabinet ministers gathered for an emergency meeting in Downing Street on Thursday, he said: “Surely the lessons of Iraq, the lessons that came from the Chilcot report, are that there has to be a proper process of consultation. Cabinet on its own should not be making this decision.”

Corbyn said he wanted to see the whole picture, but also wished to see peace in the region, which he said would require restraint by western countries and Russia.

“I want to see an end to the war in Syria That does mean America and Russia holding back, pulling back and talking to each other,” Corbyn said. “The dangers of bombing now, which could escalate the conflict beyond belief … Just imagine the scenario if an American missile shoots down a Russian plane or vice versa. Where do we go from there?”

Asked whether he opposed military action in Syria under any circumstances, Corbyn said he was “not in favour of increasing military action in Syria; what I’m in favour of is a political process to bring about peace”.

“That person needs to be removed. I mean, intervention must take place if evidence comes back that the PM or the president, or whoever the leader is, is gassing his own people. Get them out,” she said. “But I suppose what we’ve seen is it’s not as easy as that. And I think that’s where Jeremy’s position comes from.

“They always seem to abscond, end up in another country. This world is messed up. It’s not easy. But if a leader is killing their own, they need to be removed. We don’t keep them there. They need to go. He needs to be removed.”

Any parliamentary vote on military action would probably cause a significant split in the Labour party, with some MPs likely to listen more sympathetically to the case for intervention.