Keir Starmer will not lead his party into the next general election, Labour-supporting unions have predicted, in an intervention that threatens to further destabilise the prime minister after a damaging few days.

The 11 Labour-affiliated unions – which include Unite, Unison and the GMB – are expected to issue a joint statement on Wednesday saying “at some stage” the party will have to put a plan in place to elect a new leader.

At a private meeting on Tuesday, the unions were divided over whether to call for Starmer to set out a timetable for his departure, with one source telling the Guardian there had been a “big fight” among union officials.

However, they are understood to have agreed to issue a statement saying they expect there to be a change of leadership, despite GMB and Community arguing it was not in the unions’ best interests to get involved in leadership wrangling.

In a leaked copy of the statement, the unions said it was clear to them that Labour “cannot continue on its current path”, and…