Exclusive: parties will step aside for each other in 60 seats to give single pro-remain candidate a free run

The Liberal Democrats, Plaid Cymru and the Greens have finalised a plan to step aside for each other in 60 seats across England and Wales in the general election. The alliance is intended to give a free run to one pro-remain party in each constituency.

The agreement, which does not include Labour, covers 49 seats in England and 11 in Wales. It was made under the banner of a cross-party group called Unite to Remain, which has spent several months trying to broker the plan.

A so-called progressive alliance plan, also including Labour, was attempted before the 2017 election but arrangements were only made for a handful of seats, in part because of the difficulty of getting local parties to agree.

Q&A What is ‘tactical voting’? Show Hide Under the first-past-the-post voting system, tactical voting is when you vote for a party that you would not normally support in order to stop another party from winning. For example, in a constituency where the result is usually tight between a party you dislike and a party you somewhat dislike, and the party you support usually comes a distant third and has no chance of winning, you might choose to lend your vote to the party you somewhat dislike. This avoids ‘“wasting” your vote on a party that cannot win the seat, and boosting the chances that the party you dislike most will lose.

The template for the Unite to Remain idea was the Brecon and Radnorshire byelection in August, where the decision of Plaid Cymru and the Greens to stand aside helped the Liberal Democrats overturn a Conservative majority of 8,000 to take the seat.

Heidi Allen, the Conservative-turned-Lib-Dem MP, who is standing down in December’s election, was involved in organising the Brecon and Radnorshire pact and subsequently co-launched Unite to Remain.

Allen said the level of cross-party working was “unprecedented in modern British political history”.

She said: “With a single remain candidate in 60 seats we will return a greater number of remain MPs to parliament. This is our opportunity to tip the balance of power away from the two largest parties and into a progressive remain alliance.”

Allen had previously said she hoped to create deals in 70 seats, and to avoid standing against some strongly pro-remain Labour MPs.

Beyond giving the split of the seats between England and Wales, the group has not provided details of which seats will be involved, although they are billed as stretching from Cornwall to Yorkshire, and from Sussex to north Wales.

The majority of candidates given a free run will be Lib Dems given that the party had 20 MPs when parliament was dissolved this week, against four for Plaid Cymru and one for the Greens.

Peter Dunphy, the former Lib Dem treasurer who is a director of Unite to Remain, said Brecon and Radnorshire had been a successful test-case of the approach. “People want to back a winner, people want to back a contender,” he said.

He conceded that in some cases the remain alliance would be fielding candidates against sitting Labour MPs, but said the group’s main aim was to reduce the number of Brexit-backing MPs in parliament, most of whom were Conservatives. “What we have sought to do is focus on the bigger picture,” he said.

Other directors of Unite to remain include Jim Knight, a former Labour MP who is now a peer, and Jessica Simor, a prominent remain-supporting QC.

Such alliances have proved problematic in the past because of the perceived unwillingness of parties, especially Labour, to give ground. The Greens expressed scepticism about taking part in a similar process again.

However, a general election dominated by Brexit has focused minds, with some local arrangements already in place. Tthe Lib Dems in Beaconsfield have already announced they will not stand a candidate against the former Tory MP Dominic Grieve, who is standing as an independent.