UK 'moving to warfighting readiness' as it commits to build attack submarines

Sir Keir Starmer will pledge to build up to 12 attack submarines and put the military on a war footing as part of a major defence review - but without making any new spending promises.

The lack of extra cash meant the prime minister was coming under fire for empty rhetoric even before the blueprint for the future of the armed forces is released on Monday. Defence Secretary John Healey was forced to clarify that while he has "no doubt" the government will lift the defence budget to 3% of national income by 2034, he does not actually have a solid commitment from the Treasury, and this remains only an "ambition".

PM to put UK on war footing - but defence secretary 'hung out to dry by chancellor' - follow latest Sky News understands the recommendations in the Strategic Defence Review, which is expected to spell out the importance of rebuilding national defence and resilience, require investment to rise by at least that amount. Defence insiders say in reality, given the scale of what they see as the threat posed by hostile states such as Russia, funding should come even faster and be higher.

Donald Trump wants Washington's NATO allies to spend 5% of GDP on their armed forces, while Mark Rutte, the head of the alliance, is pushing for 3.5% by 2032. "The real story is that Healey didn't get the money," one source said.

A second source said there is a danger of the UK losing its leadership role in NATO if it fails to support any potential new 3.5% GDP spending target. Unusually, the government released responses from Sir Keir and the defence secretary to the review hours before the country would be given a chance to scrutinise its content.

New Sky News podcast launches on 10 June - The Wargame simulates an attack by Russia to test UK defences The document, which is understood to be around 130 to 150 pages, differs from previous reviews as it has been led by external experts rather than being carried out internally. In a statement, the government said it would commit to "a landmark shift in our deterrence and defence, moving to warfighting readiness to deter threats and strengthen security in the Euro Atlantic area".

The prime minister will also announce the UK's plans to build "up to" 12 new nuclear-powered attack submarines in a partnership with Australia and the US known as AUKUS. However, the only thing new about this is a bit more clarity on the size of the fleet.

The previous government had already committed to starting to replace the Royal Navy's Astute-class submarines by the late 2030s with AUKUS boats. "Sort of what we already know… repackaged into an announcement," a defence industry source said.

And the incumbent fleet is not even fully operational yet - almost 30 years after the first order was made. Britain's nuclear deterrent - carried by a different type of submarine - will also be an important focus of the review.

The prime minister, for the first time, put a price tag on the cost to develop nuclear warheads for the Trident missiles that will be carried by a new fleet of nuclear-armed submarines, which are also being built. Read more on Sky News:Ukraine 'had nothing to lose'UK weapons factories 'built soon''Give prison officers lethal weapons' He said the UK is spending £15bn over this parliament on the effort.

This investment, coupled with the expansion in submarine building, will support 30,000 highly-skilled jobs across the country, according to a Ministry of Defence statement. "From the supply lines to the front lines, this government is foursquare behind the men and women upholding our nation's freedom and security," the prime minister is expected to say.

"National security is the foundation of my Plan for Change, and this plan will ensure Britain is secure at home and strong abroad. "This Strategic Defence Review will ensure the UK rises to the challenge and our Armed Forces have the equipment they need that keeps us safe at home while driving greater opportunity for our engineers, shipbuilders and technicians of the future." James Cartlidge, the shadow defence secretary, criticised ministers for failing to give a firm date to lift defence spending to 3% of national income.

"All of Labour's Strategic Defence Review promises will be taken with a pinch of salt unless they can show there will actually be enough money to pay for them," he said. It was a sentiment echoed by the Liberal Democrats.

"Unless Labour commits to holding cross-party talks on how to reach 3% much more rapidly than the mid-2030s, this announcement risks becoming a damp squib," said Helen Maguire, the party's spokesperson on defence..