A union boss has warned Jeremy Corbyn it will "not go quietly into the night" if he changes Labour's policy on Trident.

GMB union leader Sir Paul Kenny gave the stark warning to the Labour leader on Monday, saying there were tens of thousands of jobs at around 50 sites in the UK that depended on defence contracts.

It came as Labour faced fresh turmoil as shadow attorney general Catherine McKinnell quit the shadow cabinet, with a warning to Corbyn that he was taking the party "down an increasingly negative path".

Her resignation is the fourth from the Opposition leader's front bench team in the wake of a contentious reshuffle which saw his left-wing supporters replace more moderate MPs and an opponent of Trident made shadow defence secretary.

Mr Corbyn said he was "happy" with the new line-up despite mounting criticism from within the ranks and the prospect of a bitter battle over his push to steer Labour to a policy of unilateral nuclear disarmament.

During last week's reshuffle, Mr Corbyn moved pro-Trident Maria Eagle from the shadow defence secretary role and replaced her with Emily Thornberry, who supports his call for Britain to disarm unilaterally.

Outgoing GMB general secretary Sir Paul said: "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 swannied away by rhetoric then they have got another shock coming."

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 £40m 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 £1.3m 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."