Jeremy Corbyn has emailed Labour Party members to ask their views on military action against Isis in Syria, as it has appears increasingly likely that the Shadow Cabinet will grant Labour MPs a free vote on the issue.

In the email, the Labour Leader says that he does not “believe that the Prime Minister made a convincing case [on Thursday] that British airstrikes on Syria would strength our national security or reduce the threat from Isis.”

“When I was elected I said I wanted Labour to become a more inclusive and democratic party,” he adds. “So I am writing to consult you on what you think Britain should do. Should Parliament vote to authorise the bombing of Syria?”

The email ends with a link for members to click through to an online form for them to submit their views to the Labour Party.

It is not clear this evening what will happen to the replies, with the Labour Party not saying whether they will published them or count the number of pro and anti-military action responses. But the email is being seen as an attempt by Corbyn to go over the heads of the Shadow Cabinet in the struggle over the party’s position on Syria.

Tom Watson publicly came out for airstrikes this afternoon, following the Shadow Foreign Secretary, Hilary Benn, who told the Today Programme this morning that he was “convinced of the case for effective action.”

The dispute has become increasingly public since the Shadow Cabinet met to discuss the issue after David Cameron’s statement on Syria on Thursday. A number of senior figures, including Watson and Benn, said they were minded to back the Prime Minister’s proposal at the meeting but no decision was taken.

Following the meeting, Corbyn sent Labour MPs a letter stating his opposition to airstrikes. He subsequently cancelled his planned trip to campaign in Oldham and spent today in London.

It seems unlikely that Corbyn will be able to secure a majority against airstrikes when the Shadow Cabinet meets on Monday, meaning a free vote is almost inevitable. It is currently unclear how many Labour MPs would then oppose military action in a Commons vote. A recent LabourList readers survey suggested that Labour Party members are opposed, with 64% of those that took part taking that position.