Jeremy Corbyn's Labour party has seen its polling figures dip further, while union backers battle over how the party should approach immigration.
Latest figures from YouGov for The Times show the party polling at 24 per cent, down from 25 per cent, itself Labour's worst performance since 2009.
The polling also shows improved performance from both Ukip and the Lib Dems, who saw their support edge upwards to 14 per cent and 12 per cent respectively.
It comes as Unite general secretary Len McCluskey – a strong backer of Corbyn – has described Labour's performance in the polls as “awful” and warned the party must improve ahead of a general election.
McCluskey told The Mirror: “Let's suppose we are not having a snap election. It buys into this question of what happens if we get to 2019 and opinion polls are still awful.
McCluskey added: “These two are not egomaniacs. They are not desperate to cling on to power for power's sake.”
Unite, which is one of Labour's biggest backers, will again elect its general secretary in April, with McCluskey facing a challenge from the union's West Midlands chief Gerard Coyne, who has today warned workers would feel “betrayed” if Britain does not axe freedom of movement.
“Theresa May and other ministers should not wait until Article 50 has been triggered to set out a negotiating position on free movement of labour. They should be saying now, without equivocation, that the issue is non-negotiable.
“There can be no compromise on the principle of taking back control of our borders,” Coyne said.