Boris Johnson could be denied election majority if third of pro-EU voters abandon party loyalty, poll finds

Boris Johnson could be deprived of a majority in the upcoming election if fewer than a third of pro-EU voters abandon party loyalty, a new survey has found.

Research for the Best for Britain campaign shows the Conservatives could win a 44-seat majority in the Christmas poll, with 364 seats, compared with Labour’s 189, 23 for the Lib Dems, three for Plaid Cymru and one for the Greens.

But if 30 per cent of voters cast their ballot tactically, it could swing the election to give pro-referendum parties a majority of four, according to a seat-by-seat analysis of 46,000 people over September and October.

In this scenario, the Tories would win 309 seats, Labour has 233, 34 for the Lib Dems, four for Plaid and one for the Greens.

If 40 per cent of pro-EU people vote tactically, the Tories would win 277 seats, Labour 255, Lib Dems 44, four for Plaid and one for the Greens – delivering a 36-seat majority for pro-referendum parties.

The SNP are assumed to win 52 out of Scotland’s 59 parliamentary seats in all scenarios, while the Brexit Party was not expected to win a single seat.

It comes as the country was on course for the first December election in decades, after a bill calling a snap poll passed its Commons stages on Tuesday. Peers are not expected to amend the bill, paving the way for parliament to be dissolved next week.

At the launch of a new tactical voting site, former Tory rebel Dominic Grieve urged people to cast aside party loyalty to fight Brexit in the election.

He said: “What is quite clear is that whilst there may be attempts of diverting attention to other issues, Brexit must be the defining issue of this election because bluntly it is likely to have a bearing on every single other topic that is going to follow.

“If Boris Johnson gets a working majority, then he will doubtless take us out of the EU very quickly, provided, particularly, now that the party has been essentially purged of most of its moderate elements.”

He admitted he could be a “direct beneficiary” of tactical voting in the upcoming poll.

Mr Grieve also confirmed reports that the Liberal Democrats had stood down their candidate in his Beaconsfield constituency to prevent the Remain vote being split. Labour is expected to stand against him, but he claimed some local Labour members would back him.

Former Lib Dem leader Sir Vince Cable said tactical voting was “not ideal” but it was a “powerful tool” to fight Brexit.

He said: “We are a ‘Stop Brexit party’ but we recognise that there are other parties who will be campaigning on that platform as well.

“There are many individual candidates who will be campaigning on that platform – Dominic is standing as an independent and it would be mad if we didn’t get behind him, we will of course 100 per cent – and that kind of thinking has to be reflected across the country.”

Labour MP Anna McMorrin also urged voters to consider ditching their party loyalty for “the fight of our lives” – a sentiment that will likely set her at odds with Jeremy Corbyn.

Pollster Lewis Baston said levels of volatility over people’s political allegiance were at the highest since the 1920s during the 2017 campaign, with 35 to 45 per cent of people switching from one party to another.

He said: “I think in 2019, we are still in this world where there’ll be massive variation between seats.

“That’s where exercises like this one, come in very handy. They are a map, not a perfect map by any means but the best thing we have mapping, where the big changes are, which parties are in contention for a seat.

“You can’t just look back at 2017 or 2015 or 2010 to see the geography and party support. It’s all changing.”

The study was carried out for Hope not Hate and Best for Britain by focaldata, a polling agency that specialises in understanding niche audiences using a technique called MRP (multi-level regression with poststratification) to estimate opinion to each constituency.

The MRP polling model was used to successfully predict the US election in 2016 and the hung parliament in the 2017 snap election.

The tactical voting tool will be found on getvoting.org.