Orders for two new Royal Navy aircraft carriers have been confirmed by Defence Secretary Des Browne.
He said the £3.8bn contract would lead to the construction of the largest vessels ever sailed by the Royal Navy.
The new 65,000-tonne carriers - HMS Queen Elizabeth and HMS Prince of Wales - will enter service in 2014 and 2016.
Mr Browne said the work would support and create 10,000 jobs across the UK, including those at yards on the Clyde, Rosyth, Portsmouth and Barrow.
The contract was described as a "major project" for the shipbuilding industry by Prime Minister Gordon Brown.
The work will be shared among a number of companies, including BAE Systems' Govan and Scotstoun yards in Glasgow, which employ 3,000 people.
The ships will be built in sections and then assembled at the Rosyth dockyard in Fife.
Making the announcement, Mr Browne said the carriers would "provide our front-line forces with the modern, world class capabilities they will need over the coming decades".
"The carriers represent a step-change in our capabilities, enabling us to deliver increased strategic effect and influence around the world at a time and place of our choosing."
However, he said the carriers could not be built without a change in the maritime sector.
"I am pleased that VT Group and BAE Systems intend to form a joint venture in naval shipbuilding and support," said Mr Browne.
"The creation of such a joint venture will enable the Royal Navy to work with the industry to deliver the infrastructure the navy will need to support the fleet in the future while retaining all three of our existing naval bases at Portsmouth, Devonport and Faslane.
"This will be good news for the three communities."
Thousands of people are employed by the Clyde yards
However, he warned there would be "some reductions" in the 17,800 personnel currently employed at the bases.
The Ministry of Defence said about 40% of the carriers work would be carried out by the joint venture between BAE Systems and VT Group - 15% in Portsmouth and 25% in Glasgow.
Thales and Babcock will each have 16% of the contract, while the remaining 28% will be carried out by BAE Systems at Barrow and by its Integrated System Technologies (Insyte) division, based in Surrey.
Shadow Defence Secretary Liam Fox welcomed the announcement but said it came at "a high price" for the navy.
"Since 1997, the Royal Navy has faced significant cuts in force levels completely at odds with the government's own strategic defence review which called for 32 surface combatants," he said.
"We welcome the retention of three of our existing naval bases, but there will be a strong suspicion that we are not being told the full story today."
Liberal Democrat defence spokesman Willie Rennie said: "I am sure the communities of the three navy bases will welcome the decision but will perhaps wait with trepidation about the potential losses in jobs."
Scottish First Minister Alex Salmond said he was pleased that the announcement would safeguard thousands of Scottish jobs.
Councillor Gerald Vernon-Jackson, the leader of Portsmouth City Council, said it would have "ripped the soul out of the city" if the navy had pulled out.
He said: "This is an absolutely wonderful and brilliant day for the city and for the campaign we have waged to try to make sure we keep the navy base here in Portsmouth.
"The presumption last August when the review was launched was that Portsmouth would close but we have been able to turn that around completely so that Portsmouth remains the home of the navy."