Internal unrest over Jeremy Corbyn's leadership of the Labour Party has flared up again, with the resignation of a shadow cabinet minister and a warning that unions will fight any attempt to adopt a unilateralist policy on Trident.
Shadow attorney general Catherine McKinnell quit her frontbench role with a warning to Mr Corbyn that he was taking the party "down an increasingly negative path".
And GMB leader Sir Paul Kenny said the Labour leader was facing a "shock" if he tried to ditch the renewal of the UK's nuclear deterrent, predicting unions would not "go quietly into the night" if members' jobs were put at risk.
Ms McKinnell's resignation is the fourth from the Opposition leader's frontbench team in the wake of a contentious reshuffle which saw his left-wing supporters replace more moderate MPs and Trident opponent Emily Thornberry appointed shadow defence secretary in place of pro-renewal Maria Eagle.
In a letter to Mr Corbyn, the former employment solicitor, who represents Newcastle North, told him she had "shared your optimism for the 'new kind of politics' you spoke so compellingly about".
But she added: "However, as events have unfolded over recent weeks, my concerns about the direction and internal conflict within the Labour Party have only grown and I fear this is taking us down an increasingly negative path."
Ms McKinnell was replaced as shadow attorney general by Hull East MP Karl Turner who is promoted from shadow solicitor general.
Mr Corbyn is to avoid a potentially hostile ride at the hands of angry MPs tonight by defying recent convention and not addressing the first meeting of the Parliamentary Labour Party (PLP) after a Commons recess.
A spokesman said the leader would not speak as the meeting - which has been the forum for severe criticism of his leadership - would be centred on the issue of floods and so shadow environment secretary Kerry McCarthy would take the lead. Asked about Ms McKinnell's resignation, the spokesman said the Labour leader would "thank her for her service".
Meanwhile, Dewsbury MP Paula Sheriff quit as Commons aide to shadow communities secretary Jon Trickett, who was one of the 35 MPs who nominated Mr Corbyn for the leadership.
Ms Sheriff said she had stepped down as Mr Trickett's parliamentary private secretary (PPS) "to focus on my campaign to defend Dewsbury & District (Hospital) from Tory cuts and my work on the Health Select Committee".
Sir Paul said there were tens of thousands of jobs at around 50 sites in the UK that depended on defence contracts.
"We are going to ask those people what they think about the Labour Party effectively shutting down their jobs," he told BBC Radio 4's World At One.
"There is a process and there are rules and if anybody thinks that unions like the GMB are going to go quietly into the night while tens of thousands of our members' jobs are literally swaneed away by rhetoric then they have got another shock coming."
Mr Corbyn has said he wants to give Labour activists a "big say" in whether the party continues to back the renewal of the UK's nuclear weapons system amid complaints that he is seeking to bypass MPs to switch stance.
He told the BBC Radio 4 Today programme that replacing the deterrent would go against the spirit of an international agreement and insisted Britain had to "make a contribution" if it wanted to live in a nuclear-free world.
"My whole election programme was based on the need for ordinary people to be able to participate much more in politics so that leaders don't go away and write policy, that executive groups don't go off and decide what the policy is, that ordinary people do," said Mr Corbyn.
The issue threatens to tear Labour apart with three shadow cabinet members - shadow work and pensions secretary Owen Smith, shadow education secretary Lucy Powell and shadow justice secretary Lord Falconer - already refusing to rule out quitting their posts if the party drops its backing for the nuclear deterrent.
Sir Paul also accused the Government of making a "direct attack" on Labour's ability to raise funds through a series of reforms he claimed could wipe up to £40 million from its coffers over the course of a parliament.
Internal party documents seen by The Guardian suggest staff will have to be laid off as a result of cuts.
Government reforms to state funding for opposition parties, known as Short money, could see it lose £1.3 million a year, while changes being made under the Trade Union Bill that would require Labour-affiliated union members to opt in to paying contributions is set to wipe out millions.
Sir Paul said: "This is a direct attack on the Labour Party's ability to raise funds."