Prime minister Andy Burnham was set to announce the funding during a visit to the BAE Systems shipyard in Barrow, northwestern England, on Thursday.
"A major £8.4bn investment in the UK's nuclear deterrent, delivering jobs and opportunity for young people for years to come," Burnham was set to announce, according to a Downing Street press release.
BAE Systems has been tasked with building four Dreadnought Class nuclear-powered submarines as part of Britain's nuclear deterrent.
Of the £8.4bn investment, BAE Systems will receive £5.9bn, while the rest will go to the wider supply chain.
According to Downing Street, the funding will help the first of the four submarines, HMS Dreadnought, complete sea trials and "be ready to enter service with the Royal Navy in the early 2030s".
It will also enable the second submarine, HMS Valiant, to reach the sea trial phase, while the third and fourth vessels continue through construction.
The programme will support 47,000 jobs and apprenticeships, according to Burnham, who has made tackling youth unemployment a priority of his administration.
The submarines "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," Burnham was set to say during his visit to the Barrow shipyard.
Defence secretary Wes Streeting said the investment "secures our commitment to deliver Dreadnought Class submarines by backing British industry".
The UK government has allocated more than £63 billion over the next four years for its nuclear deterrent under its Defence Investment Plan.
The funding includes the Dreadnought submarine programme as well as new attack submarines being developed under the AUKUS military alliance with Australia and the United States.
Burnham faces pressure from the United States and NATO allies to increase defence spending while also addressing a £4.7 billion funding gap in the UK's defence plan over the next four years.
(With inputs from agencies)
