Jeremy Corbyn was greeted by supporters at an election rally in Reading as party activists predicted wide-scale losses Peter Nicholls/Reuters

Labour is heading for a “nuclear winter” outside London as party activists north of the M25 brace for a dismal result in tomorrow’s election, according to a report.

Analysis based on testimony from Labour officials, candidates and activists, who have seen thousands of canvass returns, concluded there was “a marked improvement in London but precious little to cheer about outside”.

The report by Labour Uncut, an influential grassroots blog, suggested that despite Labour’s surge in the polls in recent weeks, the party is preparing for wide-scale losses.

It noted a striking increase in Londoners indicating that they will vote Labour, with only a handful of constituencies, including Dagenham and Eltham, remaining “very difficult” for the party.

However, in the West Midlands, Yorkshire, the North West…