Labour's shadow defence secretary John Healey today said keeping the UK's Trident nuclear deterrent is 'non-negotiable' as he signalled a split from the party's approach under Jeremy Corbyn.
Mr Healey also said Labour's support for the NATO military alliance is 'unshakeable'.
Both issues were significant points of contention when Mr Corbyn was Labour leader despite the fact retaining the nuclear deterrent and backing NATO are both long-standing party policies.
The pledges were sometimes at odds with Mr Corbyn and his supporters, with the ex-leader having been a vocal opponent of nuclear weapons throughout his career, while in 2012 he called for NATO to be disbanded.
Shadow defence secretary John Healey today said Labour's support for the Trident nuclear deterrent is 'non-negotiable'
MPs voted in July 2016 to renew the UK's Trident nuclear deterrent. HMS Victorious is pictured off the west coast of Scotland in April 2013
Mr Corbyn's approach to defence and security issues when he was Labour leader prompted claims from critics that he was unpatriotic or had an anti-Western outlook.
Mr Healey said in a speech today that the 'the hardest doors to knock' at the last general election were those with Help for Heroes or British Legion stickers in the windows.
Speaking to the Royal United Services Institute think tank, he set out his party's future 'core principles' on defence so that voters, the military and the defence industry 'know where we, as Labour's new leadership, are coming from'.
He said: 'First, Labour's commitment to Nato is unshakeable. Second, Labour's support for the UK's nuclear deterrent is non-negotiable and we want to see Britain doing more to lead efforts to secure multilateral disarmament.
'Third, Labour's commitment to international law and the UN, to universal human rights and to the multilateral treaties and organisations that uphold them is unshakable.
'And fourth, Labour's determination to see British investment directed first to British industry is fundamental; it's fundamental not just to our thinking on defence, but on the kind of society we want to build.'
Parliament voted in July 2016 to renew the Trident nuclear deterrent but the issue caused a massive Labour split as Mr Corbyn voted against renewal despite it being party policy.
Then in April 2017 he suggested he would never use the deterrent and might scrap it if he became PM.
Mr Healey also used his speech to criticise what he claimed is a £17 billion 'black hole' in the defence budget as the Government carries out its integrated review of the military.
Support for Trident renewal and for NATO are long-standing Labour policies but they were points of contention during Jeremy Corbyn's time as party leader
He committed Labour to building four nuclear submarines at Barrow-in-Furness, adding that spending on defence in the UK is a 'force for good'.
He added: 'We cannot any longer go fudging and fumbling our way into the future, with major procurement projects at the mercy of the illusion that "something will turn up" to pay for them.
'We are the party of sovereign defence capability – we see the steel industry, the shipyards, and aerospace and materials industries as a national asset.
'We want to see a clear plan from Government to enhance these capabilities.
'We want to see, for the good of our country, as much as possible of our equipment designed and built here.'