Jeremy Corbyn was embroiled in a fresh row over the renewal of Trident last night after declaring he would never launch a nuclear strike if he was prime minister.
The issue dominated the final day of the party’s conference in Brighton, with shadow defence secretary Maria Eagle branding the comments “unhelpful”.
Deputy leader Tom Watson tried to gloss over the split as he closed the annual gathering, claiming the party had avoided sliding into factionalism.
He told activists Labour spoke with “one voice” and insisted MPs had “remained friends” despite differences of opinion.
Ms Eagle said Mr Corbyn’s comment “undermined to some degree” the review she was carrying out of the party’s defence policy.
She said Labour’s current policy was in favour of retaining a nuclear deterrent, adding: “I don’t think that a potential prime minister answering a question like that, in the way in which he did, is helpful.”
In spite of the spat, Mr Watson hailed Labour as a united force.
Addressing delegates, he said: “It would have been easy for us to have slid into factionalism this week.
“We’ve shown that we can have different opinions, and argue for them passionately, but remain friends.
“It’s what normal people do in the real world and they do all the time – how often have you disagreed with colleagues at work, had a bit of an argument, but stuck to a common position? It’s called working together.
“And how often does your family put its differences aside so the whole family can face the world together? It’s called solidarity.
“And how obvious is it that what unites us as a party is far more than what divides? It’s called unity.
“From unity comes strength. That’s why we’re stronger now, as we prepare to leave Brighton, than we were when we arrived.
“We speak with one voice, we are one Labour.”
Mr Watson also used his speech to attack the Liberal Democrats, who he branded a “useless bunch of lying sell-outs”, and the “nasty Tories”, who he vowed to “kick down the road where they belong”.
Mr Corbyn later conceded he would have to “live with” Labour support for nuclear weapons if he failed to persuade the party to adopt his stance on unilateral disarmament.