Pro-Remain activists will deploy a phone app to organise members at Labour’s conference next week, in their attempt to push the party to adopt a more anti-Brexit stance.
Jeremy Corbyn will come under pressure to commit the party to back Remain in any second referendum.
The Labour leader has pledged to hold another public vote should he become prime minister.
But he has stopped short of guaranteeing he would campaign for the UK to remain an EU member.
Labour MP David Lammy said the goal of this year’s conference was to “throw the weight of the Labour movement to supporting staying in the European Union”.
The Together Against Brexit app, created by For our Future’s Sake, a youth and student-led movement which is part of the People’s Vote campaign, allows users to communicate with each other.
It will also be used to send push notifications to mobilise thousands of members for important conference votes and events - including the debate on Brexit expected to be held on Monday.
The pro-Remain campaign will kick off the conference with a Saturday seaside rally of senior Labour figures.
An analysis of the motions submitted to the party’s conference due to be held in Brighton showed that of 90 Brexit motions submitted, 81 call on Labour to back Remain.
A majority of the motions also back revoking Article 50 if necessary to prevent a no-deal Brexit.
Several high profile Labour figures including John McDonnell, Diane Abbott, Keir Starmer, Nick Brown and Emily Thornberry have all said they will back Remain.
But other figures have warned adopting an explicitly pro-EU platform could alienate voters who backed Leave at the 2016 referendum.