Brexit is fomenting a significant split in the alliance of Labour left-wing activists that keeps Jeremy Corbyn in power, because of his and the party leadership’s reluctance to commit to hold a referendum on any Brexit deal.

Jeremy Corbyn has been warned that his refusal to commit to a fresh Brexit referendum is causing Labour members to abandon to party in their droves, as its ruling body prepares to meet to decide the party's manifesto for next month's European Parliament elections.