The most senior shadow minister sacked in Jeremy Corbyn's new year reshuffle has hit out at the Labour leader's "barmy" plans to scrap Britain's Trident nuclear deterrent.
Michael Dugher, the former shadow culture secretary, condemned the party's defence review as an "unnecessary distraction" which would undermine its efforts to gain ground in the May elections.
He also warned the Labour leader not to try to "short-cut" the party's policy-making procedures in order to get the result he wanted.
Speaking to Labour activists in Birmingham, Mr Dugher said they should be taking the political fight to the Conservatives, "not picking another fight with ourselves".
"The idea that we can afford to spend a single day from now to May talking to ourselves about a divisive issue like Trident, rather than talking to the country about what this Tory Government is doing, is frankly barmy," he said.
Mr Dugher said that the party had reiterated its support for Trident renewal at the annual conference last year and there was no case for re-visiting the issue now.
"Labour party policy is very, very clear: we are in favour multilateral disarmament and the renewal of Trident.
"Only a few months ago, the Labour Party conference - still the sovereign policy-making body in the party - considered the issue again," he said.
"Not only did conference overwhelmingly decide against having another divisive debate - let's remember that the call for a debate on Trident was supported by just 0.16% of the trade union vote and only 7.1% of the CLP (constituency Labour Party) vote."
He also warned Mr Corbyn not to try to circumvent opposition to his plans - including from many of the big trade unions - via online polls of the activists who swept him to the leadership.
"We make policy in the party through our democratic structures - not by diktats from the centre. We are a movement and when it comes to making policy we want to involve everyone in that movement," he said.
"We don't make policy simply on the basis of a weekend email sent to a selection of party members where we might just have an up-to-date email address. We must not short-cut the party's democratic structures - to do so is to perform a grave disservice to our members."
He added: "There are real dangers here for Labour. For nearly three decades Labour has been committed to multilateral disarmament. We tried unilateralism before. It ended in electoral disaster then.
"There is no evidence to suggest that it won't end in disaster again. And running online plebiscites of a selection of party activists won't change these facts of political life."