An artist's impression of one of the new aircraft carriers

BAE Systems' Clyde shipyards and the Rosyth dockyard in Fife have won a substantial share of the �2.9bn work.

BAE will build one of the four main blocks of the carriers. The other three will be built at Rosyth and at yards in Barrow-in-Furness and Portsmouth.

Defence Secretary John Reid said 10,000 jobs would be created in the UK.

The Future Aircraft Carrier (CVF) programme set out by Mr Reid represents about 60% of the total project. The rest will be put out to tender, for which the yards can also bid.

It gives us a good stable workload to move forward and bring in younger people to give them a career Vic Emery BAE Systems

The two carriers are replacements for the three existing Invincible class ships.

The ships are being designed and will be built by an alliance between the MoD and BAE Systems/Thales UK.

Babcock, which owns the Rosyth dockyards, was proposed as the preferred assembly site in 2002.

The yards have been waiting for months for confirmation of the work, during which time the MoD has focused on eradicating as much risk as possible from the contract. The ships will be about twice the size of HMS Ark Royal.

The BAE yard on the Clyde, which has won part of the work

Mr Reid said the government would commit to a "demonstration phase" of the programme.

"This project is a key to the defence industrial strategy and marks the end to the boom and bust industrial cycle," he went on.

"The introduction of a managed and steady work stream will allow industry to plan efficiently and to retain the highly skilled workforce that h has contributed to the fine tradition of shipbuilding in this country.

"In addition, this project will sustain and create some 10,000 UK jobs around the country."

BAE Systems' managing director Vic Emery said the announcement would provide long-term job stability.

He added: "If you add this work to the work we already have, particularly with the Type 45 programme, it gives us a good stable workload to move forward and bring in younger people to give them a career."

People living nearby said the move would be good for the local economy.

One said: "Of course it's good news. It's going to keep the employment factory up here. It's going to make it quite considerable again, which is what you want."

Another added: "This is what Rosyth and Fife needs, which will give people jobs."