Defence chiefs signed a three billion pound contract on Thursday to build two aircraft carriers that will be the biggest warships in the Royal Navy's history, the government said.
Defence Secretary Des Browne said the project will create or safeguard 10,000 British jobs at shipyards from the Clyde to the Solent when work begins later this year.
The ships, to be named HMS Queen Elizabeth and HMS Prince of Wales, will be the biggest and most powerful ever constructed for the navy.
Each 65,000-tonne carrier will be the same size as the QEII cruise ship, and carry 1,450 crew and 40 planes.
"This is a historic day for everyone in defence," Browne said in a statement. "Today's contract signing seals the future for thousands of jobs, and ensures that we will have a Royal Navy fit for the 21st century."
The contract was signed on board HMS Ark Royal in Portsmouth.
They will be built by a consortium that includes a joint venture between two British companies, BAE Systems and VT Group. Other members include Babcock International Group and France's Thales, which designed the ships.
The work will take place at shipyards in Barrow-in-Furness, Glasgow, Portsmouth and Rosyth. They are due to enter service in 2014 and 2016.
Final signing of the British contract had been expected earlier this year, but was delayed after the defence ministry struggled to align its spending plans with its budget.
