Shadow defence secretary Nia Griffith has corrected fellow frontbencher Emily Thornberry over differing presentations of Labour's stance on Trident.
Thornberry had suggested support for the nuclear weapons system was subject to a defence review, should Labour come to power.
Griffith however, said the issue was "already settled" and that shadow foreign secretary Thornberry was wrong to suggest the party might drop its commitment to the nation's nuclear deterrent.
Labour's manifesto, which was launched on Tuesday, included support for the nuclear weapons system.
Speaking on LBC radio though, Thornberry said she was "sceptical" about Trident and that it could be up for discussion as part of a wider defence review.
"There was a time when we gave up on sabres or horses - you need to keep updating your defence policy and meeting the most pressing and obvious need," she said.
Any potential war would have to be "fought on 21st century terms", Thornberry added.
Speaking to BBC Newsnight last night, Griffith said Labour was "fully committed" to Trident and a review would look at how a Labour government would spend money as opposed to whether or not to support the nuclear deterrent.
She agreed Thornberry was wrong to suggest otherwise.
"With all due respect, Emily is not the shadow defence secretary. I am," Griffith said.
Last year, the Commons backed the renewal of Trident, by 472 votes to 117. Labour was split over the issue at the time, as 140 of its 230 MPs went against leader Jeremy Corbyn and backing the motion. Corbyn had given Labour MPs a free vote on the matter.
Corbyn has always opposed nuclear weapons.