Tactical voting by Remainers was a vital part of Labour’s success and the loss of the Conservative parliamentary majority, according to a new report by Best for Britain, an anti-Brexit organisation.

The report, published in full by the New Statesman, details how Labour did best and the Conservatives did worst when Labour was the clear Remain choice, whether because other parties stood down or the Liberal Democrats were not viable contenders.

It also shows how a small and significant slice of Conservative 2015 voters who backed a Remain vote switched to Labour in 2017 – and equally importantly, how some who voted for the first time to leave the European Union did not vote in 2017, handing Remain voters a decisive electoral advantage.

“Labour made their election gains on the back of a grassroots anti-Brexit vote and this analysis shows that Labour can extend their gains by appealing to those voters,” said Best for Britain’s chief executive Eloise Todd, “They are the factors few considered before the campaign began, but now they have the power and potential to make or break the leading parties’ electoral fortunes. Labour and Tories both need to note that with care.”