The yard dates back to the mid-19th century (Picture: PA).
A historic shipyard is to close despite a campaign to win new work to keep it open.
Babcock International said it had taken the "difficult decision" to close its Appledore Yard in Devon next year.
Thousands of people joined a march recently in support of the yard and signed a petition which was handed to the Government asking ministers to help.
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Babcock said in a statement that it would end its site lease in March 2019:
"Babcock's focus is now firmly on its workforce and its determination to protect their employment within the business.
"To that end, the company will offer relocation opportunities for all 199 Appledore employees at other Babcock facilities, 140 of whom are already on short-term redeployment to its Devonport operations.
"Babcock very much regrets having to take this course of action and recognises the impact it will have on its dedicated and professional workforce.
"The company will now engage in a consultation period, working closely with its employees and their trade union representatives during this difficult time."
A UK Government spokesperson said: "The Appledore yard has played a key role in building the nation’s two new aircraft carriers.
"We are very disappointed to hear that Babcock does not plan to renew the lease at Appledore and while this is a matter for the company, the government stands ready to support any workers affected at this concerning time.
"Babcock has said it will work to offer new opportunities to as many employees as possible and the company will continue to play a key role in the maritime sector, both in supporting Royal Navy ships and as a potential competitor in future shipbuilding projects."
On Twitter, the Shadow Defence Secretary said: "After months of uncertainty, this is devastating news for workers and their families. Govt must come forward with plan to support all those affected."
Unite assistant general secretary Steve Turner said:
"This shameful decision is a betrayal of a skilled loyal workforce and their community. It is a dark day for Appledore and UK shipbuilding.
"At a stroke, ministers could secure the future of Appledore by lifting the delay to contract the Type 31e frigate programme and guaranteeing that the Royal Navy's new fleet solid-support vessels are designed and block-built in yards across the UK.
"We urge Babcock to think again and for the Ministry of Defence to drop its ideological obsession with international competition and build support vessels for our Royal Navy ships in UK shipyards."
In 2017/18, Appledore generated around £24 million of the group's total underlying revenue of £5.4 billion.
The GMB union reacted with anger to the news, saying it was "devastating" for the workforce.
The union said 200 workers were set to lose their jobs when the yard closes, adding that the Government had offered a financial package to keep it open.
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Jake McLean, the GMB's official at Appledore, said: "This news is a devastating blow to the workforce and the local community.
"We want answers from the Government and Babcock about the package that was offered to save the yard."
The yard is the last survivor of a centuries-old tradition of shipbuilding on the north Devon estuary where the Rivers Taw and Torridge meet the Bristol Channel.
Appledore dates back to 1855, remaining in family ownership for many years, specialising in tug-boats and fishing trawlers, and making a significant contribution to Britain's war effort from 1939 to 1945.
The yard was bought in 1964 by shipping and charter holiday airline company Court Line and was later taken into public ownership by the Labour government to form part of British Shipbuilders.
It was bought in 1989 by Langham Industries.
Appledore flourished during the 1990s and earned a reputation for building specialist survey vessels.
However, the yard went into administration in 2003, with the entire 550-strong workforce made redundant.
In 2004 it was bought out of administration by DML, operator of Plymouth-based Devonport Royal Dockyard, which was itself bought by Babcock in 2007.