Published: 8:00 PM August 16, 2019 Updated: 6:21 PM September 17, 2020

A hit list has been created that will target 150 seats where Remainers can win to tip the balance against Brexit in an early general election.

Best for Britain, who ran highly successful tactical voting campaigns at the 2017 General Election and 2019 European elections, have refined their model using the most up-to-date postcode level data to produce a hit list of 150 marginal seats where tactical voting could be used to return anti-Brexit MPs ahead of an autumn general election. The dashboard is already in the process of being built and will be ready before the end of recess in early September.

The aim of the dashboard is to supplement work currently being undertaken at party leadership level to build a pro-EU Remain alliance. The idea is to make sure that where negotiations between parties break down, the Remain vote can still coalesce around a single candidate to heighten their chance of winning the seat.

Candidates will be selected based on their "Remain credentials", rather than just their willingness to back a final say on Brexit. These "Remain candidates" will be defined by their voting records, public statements or - in the case of prospective parliamentary candidates with no voting record - whether they will sign a "Remain pledge". The pledge will ask them to promise to vote for a final say with the option to remain in the EU, and then campaign to remain.

The hit list of 150 marginal seats across England and Wales will predominantly focus on the North West and Yorkshire and the Humber, where current polling suggests that a Remain alliance is needed to shift the axis of power away from a potential Tory-Brexit Party pact.

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Best for Britain have been working with Heidi Allen's Unite to Remain group to identify areas where pacts at party level are most likely to succeed, and targeting seats accordingly. The campaign will also defend key pro-EU voices such as Lib Dem MP Layla Moran in Oxford West and Abingdon, Labour MP Rosie Duffield in Canterbury and Tory MP Guto Bebb in Aberconwy.

The dashboard adds real firepower to Best for Britain's summer campaign to make sure the Remain side is ready for an autumn showdown.

The campaign has largely focused on preparing the ground for remain parties to work together after the group sent its "Grassroots guide to building the Pro-European Alliance" to 300,000 people, including over 200 local association heads.

The campaign says initial responses have been positive, with successful case studies of local parties working together due to be fed into a second edition of the document as "best practice examples".

Naomi Smith from Best for Britain warned Remainers "will not be blindsided by Boris Johnson".

She said: "A general election is looking more and more likely as Johnson wants to force through a damaging no-deal Brexit by 31 October 'do or die', against the will of parliament and the people. We need to be ready for that.

"Tactical voting will be the centrepiece of our autumn strategy and will define the next election. Using our experience of creating successful marginal-swinging dashboards in the past, we will encourage tactical voting on a scale never before seen in this country.

"If you're going to campaign to remain, you're safe. If not, we're coming for you."