Labour divisions over renewal of Trident will be "irrelevant" by the next election because the main decisions will have been made, a former cabinet minister has said.
Party leader Jeremy Corbyn fuelled tensions in the party when he suggested the UK could retain nuclear missile submarines but they would go to sea without warheads.
Dame Margaret Beckett said the suggestion was a "way of exploring other ideas" as the party tears itself apart over its future policy, but warned that the internal turmoil will be immaterial as the main decision on renewal is set to be taken this year.
She told BBC Radio 4's Today programme: "Some of this conversation, frankly, is going to be irrelevant by the time of the next election because major decisions about Trident will have been made."
Dame Margaret, who has written a report on the reasons for Labour's defeat in last year's general election, said the "biggest single problem" was lack of trust on the economy and that remained a major issue.
Labour also struggled to put across its pledges on immigration to voters against the "thuggishness" of the Tory and Ukip strategy, she said.
Dame Margaret said Labour had the "right" policy but would have to "feel our way" to an approach voters "understand".
She said: "The simple thuggishness of the Ukip and Conservative approach is easier to understand and we didn't overcome those communication difficulties."
Dame Margaret, who has previously described herself as a "moron" for helping Mr Corbyn to get on the leadership ballot papers, said "only time will tell" if he will be successful.
"Jeremy performed an unexpected political miracle in the scale of the votes he got in the Labour Party and the way in which he inspired people. If he can do that with the British people, we will be doing all right."
She insisted predecessor Ed Miliband was not solely to blame for Labour's defeat, insisting he was "very badly treated" and "still is" by the media.
"One of the biggest mistakes we could make is simply to say, 'oh, it was all because of Ed Miliband and that's fine and he's gone so now we don't have a problem'. That would be really stupid because we have a much deeper problem of trust and understanding with the British people than simply represented by Ed," she added.