Defence giant BAE Systems has confirmed that it is cutting almost 3,000 jobs at sites across the country, mainly in its military aircraft division.
The firm ended days of speculation by giving details of a huge redundancy programme, saying it needed to maintain competitiveness.
BAE said the company must "ensure its long-term future".
Research group Oxford Economics said 5,700 jobs may now be at risk at BAE's suppliers and in the wider economy.
Union leaders said BAE staff were "distraught and tearful" at the news.
BAE employs 40,000 people in the UK, and 100,000 worldwide, and the biggest job cuts will be at sites in Lancashire and Yorkshire.
The Brough factory, in East Yorkshire, will lose 900 jobs from its 1,300-strong workforce.
At Samlesbury, Lancashire, 565 jobs will go from the 3,970-strong workforce.
At Warton, Lancashire, 843 posts will be lost among 6,537 staff.
Among other plants affected are operations in Dorset, Hampshire, Surrey, and Essex.
Most of the cuts will be made in BAE's military aircraft division, which is being affected by a slowdown in orders for the Eurofighter Typhoon fighter aircraft.
Mr 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."
He said changes in the US defence budget would also affect BAE's workload.
Unite, the biggest union at BAE, said it would meet management on Tuesday "and we will be doing everything we can to mitigate the impact of these cuts."
The union said in a statement: "The government cannot sit on its hands and allow these highly skilled jobs to disappear."
Business Secretary Vince Cable said his department would do everything it could to ensure that valuable skills were not lost the the UK economy.
"This news from BAE Systems will be a serious knock to the individuals and communities affected," he said.
TUC general secretary Brendan Barber told the Labour Party conference in Liverpool that the job losses were "yet another devastating body blow to our manufacturing base".
Senior Labour and Conservative MPs Alan Johnson and David Davis, who have BAE plants in their constituencies, criticised the company for the way it handled the news.
Mr Johnson said that after days of media speculation, it had been a case of "terrible news delivered in the worst possible way".
Mr Davis said BAE management "should be ashamed of itself".