Three Remain-backing parties have revealed the 60 target seats where they will stand down to boost the chances of electing anti-Brexit MPs in the December election.
The Liberal Democrats, Green and Plaid Cymru will not stand against each other in target constituencies around the UK.
Foreign Secretary Dominc Raab will be under threat in his Esher & Walton constituency, as the Greens step aside for the Liberal Democrats during the December 12 poll.
Jo Swinson's party hopes to challenge the 39-point lead secured by Mr Raab in the last General election, as polls show voters shifting towards the Lib Dems in the commuter belt around London.
They will also be free to challenge Zac Goldsmith's Richmond Park constituency, which he lost to them in a 2016 by-election, only to win it back eight months later, as well as Guildford, South West Surrey, Hitchin & Harpended, Tunbridge Wells, Watford, Cheltenham, Finchley & Golders Green and Heidi Allen's former South Cambridgeshire seat.
The Green Party will be given a free run at Brighton Pavilion, a seat held by Caroline Lucas since 2010, as well as Dulwich and West Norwood, which will be contested by the party co-leader Jonathan Bartley.
The 'Remain alliance' will also target 12 seats in Wales, where Plaid Cymru will stand aside for the Liberal Democrats in Brecon and Radnorshire, Cardiff Central and Montgomeryshire.
This would put former Welsh Secretary Alun Cairns under threat as the Lib Dems and Plaid Cymru allow the Greens to contest his Vale of Glamorgan constituency.
The Liberal Democrats confirmed they are also stepping aside in Beaconsfield, where prominent Remainer Dominic Grieve is fighting his seat as an independent after being expelled from the Conservative party.
The full list of seats fought by each party:
England
Green Party: Brighton, Pavilion, Isle of Wight, Bristol West, Bury St Edmunds, Stroud, Dulwich and West Norwood, Forest of Dean, Cannock Chase, Exeter.
Liberal Democrats: 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.
Wales
Green Party: Vale of Glamorgan.
Liberal Democrats: Brecon and Radnorshire, Cardiff Central, Montgomeryshire.
Plaid Cymru: Arfon, Caerphilly, Carmarthen East and Dinefwr Dwyfor, Meirionnydd, Llanelli, Pontypridd, Ynys Mon.
