I am hopeful that Labour will back a Final Say, putting it on the right side of history and potentially saving our country from this mess

Now that we’re just six months away from the day we’re scheduled to leave the EU, the case for a final vote on the Brexit deal has never been stronger. Happily, the campaign to give that to the people has never been stronger either. Hundreds of thousands of us have mobilised over the summer, including in these pages, where The Independent launched its Final Say campaign. Now poll after poll finds the public in favour of a vote, with many favouring the option to abandon the growing chaos and stay in the EU.

Over the next weeks and months we have to keep building this momentum. If we do, we can win a people’s vote on the final terms of the deal. Not since the buildup to the invasion of Iraq have I seen as many people on the streets, demanding a stop to a disastrous plan from the government, as I did on 23 June for the last People’s Vote march. And, with thousands of Greens, I’ll be joining at the next demonstration on Saturday 20 October.

This week the People’s Vote campaign published a new report with a roadmap that sets out the democratic routes in parliament through which the decision to hold a vote on the final outcome could be reached. There are variations on two main scenarios: either with a majority of MPs demanding a final say, or events descending into such chaos that another referendum becomes the only way for the prime minister to hoist herself out of the quicksand. It seems to me that securing a final say from our citizens in such circumstances relies on two things: clear public backing for a vote on the final decision and real support from the opposition.

The public’s growing concern is plain to see. The more people see of Brexit, the less they like it. Just this week polling found only a quarter of Daily Mail readers think Britain will get a good Brexit deal – while the IMF warned on Monday that a no-deal, crash-out Brexit would deliver “reduced growth, an increase in the [budget] deficit and a depreciation of the currency”. Polls show more and more constituencies that voted to leave in 2016 would now back the reverse, and thousands of new people are signing this site’s petition for a Final Say every week. That means that a key remaining problem is getting the leadership of the main opposition party, Labour, to speak clearly for the extra democracy the public wants.

But we have progress there, too. When politics hits a point of stubborn deadlock like this, it’s easy to feel hopeless, but progress can be made when the arguments are strong and politicians listen to each other. I proposed a motion to the London Assembly, supported by Lib Dem assembly member Caroline Pidgeon, calling on Mayor Sadiq Khan to support the call for a people’s vote. On the day of the meeting, Labour AMs joined us and the cross-party motion was passed. This was followed the next weekend by the mayor doing exactly what we asked and making a strong statement in support of the final say the country needs.

This weekend, we will hit a key moment in the call for a people’s vote: Labour Party conference. Until now, Jeremy Corbyn as Labour leader has remained steadfast in his refusal to engage with calls to support the People’s Vote campaign. As the co-leader of a political party myself, I can understand the temptation to stay the course and cross his fingers in the hope of a general election. I can also appreciate the difficulties of bridging distinct bases of voters who fell on different sides of the 2016 referendum question.

But the Labour leadership is showing signs of willingness to choose the right side of history. Figures like shadow chancellor John McDonnell have prepared the ground by saying that a people’s vote is “on the table”. Unions are coming out in support. Even allies like Paul Mason have set out their own roadmaps of how Corbyn can call for a people’s vote, while maintaining Labour’s broad coalition of support. And now an unprecedented number of constituency party motions are being taken to Labour conference, forcing the issue onto the agenda.

If this debate is held at Labour conference, as seems likely, I am hopeful that the avalanche of politicians seeing sense and calling for this decision to go back to the people will continue, and that we will see that decisive shift in Labour’s position. With clear public support combined with real agitation from the opposition in the House of Commons, we would finally have the tools we need to pull ourselves out of the wreckage of the government’s negotiations and save our future as European citizens, part of the biggest project for international unity, cooperation and peace ever created.

The People’s Vote and Final Say campaigns have set out the plausible paths towards a vote on the final deal. Our task, before the next six months is up, is to bring one of these scenarios to life. I’ve never been more optimistic that as a country we will succeed and survive this chaos.

Sian Berry is the co-leader of the Green Party