Chancellor George Osborne has announced a £500m investment for the Faslane naval base in Scotland, home of the UK's nuclear deterrent.
The 10-year programme, which will begin in 2017, will secure 6,700 jobs and create thousands more, Mr Obsorne said.
The money will fund the construction of sea walls, jetties and other projects as it gets ready to host the country's entire submarine fleet.
The SNP criticised the move, saying the Chancellor "has his priorities all wrong".
Faslane, located around 40 miles from Glasgow, is home to missile-carrying Vanguard submarines and recently welcomed the third of seven planned Royal Navy Astute class attack submarines.
The Ministry of Defence is also expected to base the Successor class on the Clyde when they come into service from 2028, with crews and engineers potentially calling Faslane home until at least 2067.
The base's 6,700 military and civilian staff and contractors is expected to increase to about 8,200 by 2022.
Mr Osborne said: "Today's announcement of more than £500 million demonstrates the UK Government's commitment to investing in the infrastructure and capability to ensure that Faslane remains the centre of UK submarine operations for the next generation.
"There will be thousands more jobs right here in Faslane, as well as across the UK supply chain. Across Scotland, around 12,600 people work in defence and my defence spending commitments will secure these jobs and provide huge opportunities for defence, security and technology companies all over the UK."
Scottish National Party leader Nicola Sturgeon criticised Mr Osborne for pre-empting the outcome of a vote on the renewal of the Trident nuclear deterrent, which is due to be decided by MPs next year.
SNP Westminster defence spokesperson Brendan O’Hara MP said the Government was wrong to invest in "an unwanted and obscene arsenal of nuclear weapons”.
He said: "There is something fundamentally wrong with Westminster’s values and priorities if the Chancellor thinks wasting billions on nuclear weapons is something to boast about when people are dying within our benefits system.
"Investment in Faslane is welcome - but it must be as a conventional base - and not more money spent on weapons of mass destruction."