The Dreadnought-class submarines will replace the UK’s four Vanguard-class vessels that have been in operation since 1992, carrying Trident missiles to provide a nuclear deterrent.
Those Vanguard submarines are due to be retired in the 2030s, with the Dreadnoughts entering service at the same time.
The project has taken 20 years to get to this stage and was first announced in 2006 by the then Labour Prime Minister, Tony Blair. A decade later, in 2016, MPs formally approved building the new submarines.
Thursday’s announcement of £8.4bn marks the start of what has been called the fourth phase of the project.
The spending was already planned, and was included in the Defence Investment Plan, published in the final days of Sir Keir Starmer’s government.
The plan set out £63.6bn over the next four years for what is called the Defence Nuclear Enterprise.
The bulk of the money (£47bn) will go on keeping the nuclear submarines in operation, continuing with the Dreadnoughts, starting work on what might replace them in 30 years’ time, and constructing several other new submarines and upgrading the UK’s naval docks and manufacturing facilities.
The prime minister will use his visit to Barrow-in-Furness to stress how defence spending can have economic benefits for the country.
“The submarines produced in Barrow will protect Britain for decades to come, and the 47,000 jobs and apprenticeships will change lives both in this town and in dozens of places like it,” he said prior to his visit.
“British money, spent on British workers, British firms and British skills, in the places that were written off for 40 years.”
The government says the spending on the UK’s nuclear defence currently supports around 47,000 British jobs – and is forecast to rise to 65,000 by 2030, including 22,000 apprenticeships by 2035.
Since becoming prime minister, Burnham has said he wants to reduce the number of young people not in employment, education or training and has announced funding to help those starting apprenticeships.
In a further step, Burnham has said the public procurement process, used to decide how to spend taxpayer cash, will favour companies offering 45-day work placements.
Speaking to the Jimmy’s Jobs of the Future podcast,, external he said there would be “more social value weighting in public contracts”, with a particular focus on firms offering such placements.
He said the move had been inspired by his time as Greater Manchester mayor, when he oversaw a rise in the number of 45-day placements offered by private firms.
But the announcement offered little detail of the extent of the changes, how they would be implemented and how many firms he expected to roll out the placements as a result.
Liberal Democrat defence spokesperson James MacCleary called for the use of defence bonds to “raise dedicated funding to rebuild capabilities across the whole of the armed forces”.
For Reform UK, Danny Kruger dismissed Burnham’s announcement as a “rehashed spending plan” that did “nothing to address the crisis in the UK’s nuclear programme”.
“If the Prime Minister actually cared about keeping Britain safe and ensuring our Armed Forces can stand alongside our allies, he would commit to a significant increase in spending and a total overhaul of both procurement and the nuclear enterprise,” Kruger said.
Green Party Westminster leader Ellie Chowns questioned the decision to spend billions of pounds on “weapons that must never be used”.
“Ministers should not pretend that the best way to create employment is by funnelling ever-increasing sums into the nuclear weapons programme,” she said.