Anti-Brexit campaigners have announced the 25 marginal constituencies which they will target to prevent Boris Johnson from winning a landslide majority in the election.

A new group, Vote for a Final Say, said it would pump thousands of pounds into each seat to fund social media adverts and other campaigning to help Labour, Liberal Democrat and SNP candidates defeat their Tory rivals.

All of the seats – from Labour Leave heartlands in the north to Lib Dem targets in the south – are currently on a knife-edge according to new polling.

The 25 constituencies, which include 17 Labour-held seats, 7 Lib Dem targets and one SNP target, were identified by an unpublished survey that uses the multi-level regression and poststratification (MRP) statistical technique.

MRP advocates claim it provided the most accurate polls in the 2017 election and the latest data analysis of tens of thousands of voters across the country found that large numbers of Remain supporters were at risk of wasting their vote on third-placed candidates.

The surge in young people registering to vote ahead of the deadline of November 26 has also influenced the targeting of which seats are most in play.

The technique also found key voting groups – young people, working class women and ethnic minorities – who are the least likely to participate in elections but who can be mobilised when it becomes clear that Johnson could win again.

Various tactical voting websites have been produced in recent weeks, with the People’s Vote campaign listing 100 key seats.

But the new survey by Vote for a Final Say sets out what it believes is a more realistic clutch of seats that would benefit from a ‘laser-like’ focus given the threat they face from the Tories.

The People’s Vote campaign recently descended into bitter in-fighting over its strategy and tactics, and activists believe that with just 16 days to polling day there is a need to offer voters more clarity.

James McGrory, the former director of the People’s Vote campaign and a senior adviser to Vote for a Final Say, said: “Time is running out to stop Boris Johnson getting a landslide.

“There have been too many arguments about who has the best tactical voting website or polling data and not enough action. We can all agree that these 25 seats are critical if we’re to prevent Brextremist Tories securing total power. Now is the time for everyone to roll their sleeves up and start fighting back.”

Amanda Chetwynd-Cowieson, the co-founder of For our Future’s Sake, added: “More than a million young people have registered to vote in this generation-defining election over the last few days. Now we must make sure people use those votes – and use them wisely.

“Young people are traditionally the group of voters least likely take part in elections but we also have the most to lose. In constituencies where just a few hundred people could make all the difference, it is vital we make our voices heard.”

The complete list of 25 constituencies – with the best-placed anti-Brexit candidate recommended in each – is as follows:

Birmingham Northfield, Richard Burden (Lab)

Bristol North West, Darren Jones (Lab)

Bury North, James Frith (Lab)

Cambridgeshire South, Ian Sollom (LD)

Canterbury, Rosie Duffield (Lab)

Cardiff North, Anna McMorrin (Lab)

Cheadle, Tom Morrison (LD)

Cheltenham, Max Wilkinson (LD)

Croydon Central, Sarah Jones (Lab)

Eltham, Clive Efford (Lab)

Enfield Southgate, Bambos Charalambous (Lab)

Finchley & Golders Green, Luciana Berger (LD)

Gower, Tonia Antoniazzi (Lab)

Ochil & South Perthshire, John Nicolson (SNP)

Portsmouth South, Stephen Morgan (Lab)

Reading East, Matt Rodda (Lab)

Sedgefield, Phil Wilson (Lab)

St Albans, Daisy Cooper (LD)

Wakefield, Mary Creagh (Lab)

Warrington South, Faisal Rashid (Lab)

Warwick & Leamington, Matt Western (Lab)

Weaver Vale, Mike Amesbury (Lab)

Wimbledon, Paul Kohler (LD)

Winchester, Paula Ferguson (LD)

Wirral West, Margaret Greenwood (Lab)