In today’s Guardian, our Layla Moran, Green MP Caroline Lucas and Labour MP Clive Lewis argue that we need progressive parties to come to an arrangement to beat the Tories.

Meanwhile the rightwing parties have consolidated, after the Tories swallowed the Brexit party whole. But progressives remain split, competing for the same voters – we divide; they conquer.

And yet poll after poll shows there is a progressive majority. We need to shape and win that majority.

This is why citizens are now using their votes wisely, to back the best-placed non-Tory; and why, under the radar, local parties are campaigning tactically to best direct their resources.

They argue against the tribalism that prevents progressive parties working together:

Old politics holds us back. The Labour rulebook demands the party stands candidates in every seat, regardless of whether doing so guarantees another Tory win. Local parties should be allowed to decide. But tribalism runs deep everywhere, and trust takes times to grow, with the inevitable result of another likely general election loss. We cannot allow that to happen. This self-defeating tribalism must go. While well-intentioned, party bureaucracies could be the last bastions of the old politics to fall. If this needs to be a grassroots alliance, then so be it.

Part of the problem with the idea of a progressive alliance was that loads of people think it’s a fab idea, but nobody has been able to set out how it might work in practice. But in recent years, there have been some good examples of where parties have worked together to our mutual gain.

Layla’s arrangement with the Greens in Oxfordshire has helped both parties and hurt the Tories badly. From Lib Dem wins in Oxford West and Abingdon in 2017 and 2019 to a joint administration of Lib Dem Labour and Green ousting the Tories from power in Oxfordshire County Council in May this year, this is a shining example of how a progressive alliance can work in practice. The test will be whether they can govern as cleverly as they have campaigned.

During the leadership election last year, Layla talked about how she had made great efforts to win over the Greens in the run up to her win in 2017. She went along to their meetings and talked to them and answered some tough questions. She put the effort into building up strong relationships with them on the ground.

However, the Unite to Remain effort at the 2019 election was doomed to failure, mainly because Labour refused to get involved and partly because it was imposed on seats in a way that was never going to work.

The last time Caroline Lucas faced a Lib Dem in her Brighton Pavilion seat was in 2015. Her then opponent Chris Bowers went on to co-edit The Alternative, an argument for a more progressive politics with her and Labour’s Lisa Nandy. I interviewed both Chris and Caroline for Lib Dem Voice back in 2016.

No progressive alliance would work without the co-operation of the Labour Party. In 1997, we and Labour by and large kept out of each other’s way except in places like Chesterfield where we were genuinely fighting each other for the seat. I was involved in that campaign and our move forward then put us in pole position for Paul Holmes to win in 2001.