BAE Systems has confirmed it is cutting almost 3,000 jobs at sites across the country, mainly in its military aircraft division.
BAE, which employs around 40,000 workers in the UK, said the cuts had been driven by the need to stay competitive. The biggest job cuts will be at sites in Warton and Samlesbury in Lancashire and at Brough in East Yorkshire, although jobs will also be lost at the firm's head office in Hampshire.
Ian King, chief executive of BAE Systems, said: "Our customers are facing huge pressures on their defence budgets and affordability has become an increasing priority. Our business needs to rise to this challenge to maintain its competitiveness and ensure its long-term future."
BAE said the potential job losses were: 899 at Brough, East Riding of Yorkshire; 51 at Christchurch, Dorset; 78 at Farnborough, Hampshire; 74 at Filton, Bristol; 81 at Frimley, Surrey; 26 at Great Baddow, Essex; 35 at Hillend, Fife; 21 at Loughborough, Leicestershire; 7 at Malvern, Worcestershire; 19 at New Malden, Surrey; 565 at Samlesbury, Lancashire; 843 at Warton and Preston, Lancashire; 132 at Yeovil, Somerset; 102 at other UK locations including Royal Air Force bases; 9 in overseas locations.
BAE announced that it had started a consultation about ending manufacturing at the Brough site, which currently employs 1,300 workers. The firm said most of the job cuts would be in its military aircraft division, which is being affected by a slowdown in orders for the Eurofighter Typhoon combat jet.
King said: "Some of our major programmes have seen significant changes. The four partner nations in the Typhoon programme have agreed to slow production rates to help ease their budget pressures.
"Whilst this will help extend our production schedule and ensure the production line stays open until we receive anticipated export contracts, it does reduce the workload at a number of our sites.
"Pressure on the US defence budget and top-level programme changes mean the anticipated increase in F-35 production rates will be slower than originally planned, again impacting on our expected workload.
"To ensure we remain competitive, both in the UK and internationally, we need to reduce the overall costs of our businesses in line with our reduced workload.
"The proposals announced today aim to put the business into the right shape to address the challenges we face now and in the future and ensure we are in the best possible position to win future business.
"This transformation process is not going to be easy. We understand that this is a time of uncertainty for our employees and we are committed to working with them and their representatives to explore ways of mitigating the potential job losses."
Unite union national officer Ian Waddell said: "After days of speculation and rumours, our worst fears have been confirmed. It's a dark day for thousands of skilled men and women across the country and it is a dark day for British manufacturing.
"BAE Systems have dealt a hammer blow to the UK defence industry and Unite is determined to fight the cuts.
"Last year the UK defence industry generated over £9 billion of revenue from exports alone. Britain cannot afford to risk the future of this highly skilled industry.
"The Government's defence review has led to deep cuts in defence spending and significant job losses, meaning it will be difficult to redeploy the jobs now at risk.
"We will be doing everything we can to mitigate the impact of these cuts.
"The Government cannot sit on its hands and allow these highly skilled jobs to disappear. We expect the MoD to intervene urgently to protect these jobs, otherwise the UK's defence industry risks losing the critical mass it needs to maintain its reputation as a world leader in defence manufacturing.
"Once again George Osborne's proclamation that he would create the right conditions to drive the economy forward through British manufacturing is ringing hollow.
"The makers are not marching, they are in retreat.
"This Government must act urgently to get British manufacturing on track."
The potential job losses at Brough, Samlesbury, Preston and Warton, affecting both the military aircraft division and the head office, are linked to the changes in Typhoon and F-35 production, said BAE, while those at Christchurch, Frimley, Hillend, Malvern, New Malden and Yeovil are associated with reducing workload on information programmes.
BAE said the potential job losses at Farnborough have been driven by a reduction in Harrier and Tornado work, and job cuts at Royal Air Force bases and overseas by changes to the support requirements for Harrier and Tornado.