Published: 9:48 AM December 8, 2019 Updated: 6:08 PM September 17, 2020

Lord Michael Heseltine on stage during the Final Say rally at the Mermaid Theatre, London. Photograph: Yui Mok/PA Wire. - Credit: PA

Campaigners for a final say referendum have launched a new app which they hope will 're-open conversations about Brexit' ahead of polling day.

In 25 ultra-marginal constituencies, where just a few hundred votes could yet stop Boris Johnson's destructive Brexit, people are being encouraged to talk to friends, neighbours and family ahead of an election that could decide the fate of an entire generation.

The 'Final Say' app - created by Vote for a Final Say - provides tactical voting recommendations - identifying which candidate backing a new referendum is best-placed to win - and gives people a tool to re-open the Brexit conversation.

Campaigners say that the app goes further than existing tactical voting guides by helping to test whether messages are reaching the right people and are effective.

The app has been developed in partnership with 89up, Europe's first impact agency. It allows activists to record details about voting intention on their device, meaning they can use it to speak to people on the doorstep, in the pub or even in the living room.

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The app is being used this week as activists from youth campaign For our Future's Sake on the streets in marginal seats in St Albans, Cheltenham and Hendon.

It can be accessed at final-say.com.

Amanda Chetwynd-Cowieson, co-founder of For our Future's Sake, said: "In dozens of constituencies around the country, this election is balanced on a knife edge and there are just a few days left if we are to stop Boris Johnson getting total power.

"The most effective way of persuading people is to talk to them. At a time of year when millions of voters will be heading home for Christmas, we want to encourage families and friends to discuss how Brexit will impact on all our lives.

"Whether it's young people asking their grandparents to think about the next generation or friends at the pub discussing how Johnson's Brexit could damage their community, people need to discuss this bitterly contentious issue before they vote.

"Too often politicians are stuck on broadcast, shouting their message ever louder in a bid to get heard, but politics is at its most powerful when people talk to each other, seek to convince and change people's minds, and listen to the other side of the argument. That's especially true in the most marginal constituencies where a few hundred votes separate the candidates, in these places just a few dozen informed conversations could make all the difference."

Mike Harris, chief executive of the company 89up behind create the app, said: "Political campaigns like to scrape data off the internet and then often clumsily target messages at voters. We are helping Vote for a Final Say use information collected in real conversations to test which messages work best and whether they are going to the right people.

"The use of technology in political campaigning has become increasingly controversial over recent years. But, used in the right way, people do not just have to be rows and rows of dots on a screen. Instead, campaigns like Vote for a Final Say and For our Future's Sake want to build a better politics based on what real people say in real conversations."