Pro-EU candidates have said they are “putting party politics aside” at the launch of a pact under which they have agreed not to stand against each other in 60 seats at the general election to avoid splitting the remain vote.
The Liberal Democrats, Plaid Cymru and the Green party said they would give voters one “remain choice” across England and Wales, with candidates standing aside in seats in Brighton, Exeter and Bristol, parts of London and the south-west, and 11 of Wales’s 40 constituencies.
The project, called Unite to Remain and led by the former MP Heidi Allen, was launched more widely on Thursday after its initial success in the Brecon and Radnorshire byelection earlier this year. The Greens and Plaid Cymru stood aside for the Lib Dem candidate in that seat, ousting the sitting Conservative, Chris Davies, in the process.
Allen, who is leaving politics at the election after spells with the Tories, Change UK and the Lib Dems, said: “This is a Brexit election, and staying in the European Union is possible, and this is the deciding moment.
“We are putting party politics aside in the interest of our country and [we have] cemented a cross-party arrangement whereby remain-voting parties in England and Wales are working together to back one remain candidate.
“With a single remain candidate in each of these seats, we can deliver a greater number of MPs into parliament. This is our opportunity to tip the balance of power away from the two largest parties and into the progressive remain alliance.”
The Lib Dems will not challenge the Green party in Brighton Pavilion, which Caroline Lucas is defending. The party did the same in the 2017 general election. The Greens will also field the only “remain candidate” in eight other seats in England, and Vale of Glamorgan in Wales.
The Lib Dems are expected to benefit most from the arrangement, given the Greens will stand aside in 40 seats in England, and Plaid and the Greens will stand aside in three seats in Wales. Among the seats in England are Tory-held Watford, Esher and Walton, and Chelsea and Fulham.
The Lib Dem leader, Jo Swinson, said it was only possible to build a brighter political future “if we are prepared to work alongside others”. Adam Price, the Plaid Cymru leader, said the strategy was “grownup politics”.
The Greens and Lib Dems will stand down in favour of Plaid in Arfon, Caerphilly, Carmarthen East and Dinefwr, Dwyfor Meirionnydd, Llanelli, Pontypridd and Ynys Môn.
Unite to Remain said it had approached Labour about being part of the process, but had been rebuffed. Asked about the pact, the shadow chancellor, John McDonnell, said: “We will never enter pacts, coalitions or deals like that. Ever.”
After a speech in Liverpool, McDonnell condemned the Lib Dem role in the 2010-15 coalition government with the Tories.
“I’d just say this to those Greens and others who are getting into bed with the Lib Dems: I remember what the Lib Dems did when they were in government. I say, go and ask any disabled person in this country who went through the brutality of the work capability assessment,” he said.
Unite to Remain’s directors include the Labour peer and former cabinet minister Jim Knight and the remain-supporting QC Jessica Simor.
Full list of remain candidates
England
Green party (Lib Dems standing aside)
Brighton Pavilion
Isle of Wight
Bristol West
Bury St Edmunds
Stroud
Dulwich and West Norwood
Forest of Dean
Cannock Chase
Exeter
Lib Dems (Green party standing aside)
Bath
Bermondsey and Old Southwark
Buckingham
Cheadle
Chelmsford
Chelsea and Fulham
Cheltenham
Chippenham
Esher and Walton
Finchley and Golders Green
Guildford
Harrogate and Knaresborough
Hazel Grove
Hitchin and Harpenden
North Cornwall
North Norfolk
Oxford West and Abingdon
Penistone and Stocksbridge
Portsmouth South
Richmond Park
Romsey and Southampton North
Rushcliffe
South Cambridgeshire
South East Cambridgeshire
South West Surrey
Southport
Taunton Deane
Thornbury and Yate
Totnes
Tunbridge Wells
Twickenham
Wantage
Warrington South
Watford
Wells
Westmorland and Lonsdale
Wimbledon
Winchester
Witney
York Outer
Wales
Green party (Lib Dems and Plaid Cymru standing aside)
Vale of Glamorgan
Lib Dems (Greens and Plaid Cymru standing aside)
Brecon and Radnorshire
Cardiff Central
Montgomeryshire
Plaid Cymru (Lib Dems and Greens standing aside)
Arfon
Caerphilly
Carmarthen East and Dinefwr
Dwyfor Meirionnydd
Llanelli
Pontypridd
Ynys Môn
