LABOUR MPs will be given a free vote on Trident, according to Len McCluskey, leader of the country’s biggest trade union Unite.

Mr McCluskey claimed to have been told privately by Jeremy Corbyn’s office that this would be the UK Labour Party’s position, which some will doubtless believe would undermine the review of policy currently being undertaken by Emily Thornberry, the shadow defence secretary. However, while allowing a free vote would remove any formal rebellion against a whipped line on policy, it would open the party leadership to accusations of weakness on the key subject of the defence of the realm.

While Labour in Scotland has come out against renewing Britain’s nuclear deterrent, thus placing it at odds with its leader Kezia Dugdale, Labour across the UK is supportive but conducting a review. An interim report is due in the summer with a vote expected at the party’s annual conference in the autumn. Of course, Jeremy Corbyn is vehemently opposed to renewal and has made clear if he became prime minister, he would never press the nuclear button.

But the Unite General Secretary, whose union is strongly in favour of renewing Trident, largely predicted on saving thousands of defence jobs, told The Guardian: “What I’m expecting to happen, and what I am told will happen, and Jeremy should announce this and be clearer about it, is that Labour MPs will be given a free vote.

“So that’s the end of any division; people will be able to vote in accordance with their passion. That will mean that the Trident replacement submarine and their successor submarines will go through comfortably in parliament.”

Read more: Trade union's call to 'back the bomb' puts Labour splits on Trident at heart of election​

Asked if he has been told by the leader’s office that this was to be the case, Mr McCluskey replied: “Absolutely. My understanding is that the Labour leader is in favour of a free vote for MPs and the quicker everybody knows that, the quicker the media can’t try to prise any divisions.”

While it will be argued Mr McCluskey’s intervention undermines the policy review, the trade union chief insisted it was still relevant because Labour needed a new defence strategy while the UK Government appeared to have no strategy at all.

“Currently 12 per cent of the defence budget goes to the US to sustain US jobs but that proportion will go up to 25 per cent in five years,” noted the Unite leader. “What Labour should be doing is demanding from the PM that he commits to spending taxpayers’ money here in the UK; it is an outrage that it is going elsewhere,” he added.

Asked about Mr McCluskey’s claim, Labour refused to comment, saying: “We do not comment upon whipping arrangements.”

In November, Labour MPs were told to abstain on a Trident vote set down by the SNP but 14 defied the whips and voted for renewal of the £31 billion programme.

A formal vote on the UK Government’s proposal for renewal is now expected in the autumn after MPs return from the party conferences. With Labour split on the issue, David Cameron is expected to win the vote comfortably.