Image caption The union says those dropping their jobs are typically younger employees
Tata Steel will be mothball element of its plant in Newport for the 3rd time in six many years with the loss in a huge selection of tasks.
Community union said 250 jobs tend to be to go, mainly at Llanwern, which hires 1, 500 employees.
Tata stated it necessary to "reduce expenses and concentrate on production higher-value services and products".
The Welsh federal government said it could consider how it may help Tata, calling the headlines "extremely disappointing".
A spokesman added: "we continuously lobbied the UK federal government for immediate activity to handle issues such as for instance high energy expenses which can be disadvantaging the metal industry throughout the UK against our overseas competitors."
Tata will never confirm the actual quantity of task losings but stated these were mainly company and agreement employees.
The GMB union called it "more bad development when it comes to metal industry" while Unite stated job losses were "very disappointing".
Media captionDr Kath Ringwald, of University of Southern Wales in Newport, describes Tata's difficulty
This is the 3rd time in six many years that parts of the Llanwern metal processing plant were mothballed as a result of market conditions.
Regarding earlier events, work was stopped for between nine and 10 months.
Community union, which includes many members at Llanwern, acknowledged Tata ended up being under "huge pressure to lessen expenses" but stated laying off workers had been "extremely regretful".
The work losses will involve fixed-term agreement and agency workers although the union stated these included those who was indeed working in the plant for a number of many years.
Sue Lewis, regional organiser, said: "We saw these primarily younger employees as future of Llanwern plus the metal business in Newport so we're devastated at these task losings.
"We also need to remember that for every worker utilized at Tata, three jobs outside also be determined by those employees, therefore it is the ripple impact throughout the community."
Tata features verified several of its coil processing services, like the hot strip mill, will "come out of production" but included that they would-be retained to enable them to be "restarted in more favourable market conditions".
The company also said workers at Llanwern will be redeployed inside the business.
Tata currently uses 6, 950 employees at five flowers in Wales.
Media captionBBC Wales business correspondent Brian Meechan explains more about just what the statement means
Testing by Brian Meechan, BBC Wales business correspondent
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Steelmaking is a challenging business. It faces two main issues. Firstly, domestically you have the cost of making steel in the UK which is driven in no small-part by power prices, that are more than other areas of Europe.
We also need to glance at the price of metal from around the world. We've seen using the Chinese economic climate slowing down more metal is available from China as it's not necessary just as much indeed there. That steel is making its method here being bought since it is less expensive, although not exactly the same high quality. This might be having a direct effect not only on metal producers in britain but across European countries.
Tata made plenty of investment including a fresh blast furnace in Port Talbot which makes it cheaper to create steel. Most of the staff - as opposed to the fixed term employees - from Llanwern have been moving truth be told there. Processing work will remain at Llanwern.
WHAT HAPPENS with LLANWERN?
Hot strip mill - this reheats semi-finished pieces of metallic to close melting point after which rolls them thinner and longer and they're offered as coils. That is being mothballed.
Pickle range - this eliminates oxide scale which forms when the metal is rolled. Additionally it is rinsed and dried before completing. Certainly one of Llanwern's two outlines will close.
Cool strip mill this process compresses and squeezes metallic at room-temperature, reducing its thickness and improving its surface and energy. This might be being mothballed.
Galvanising line - a layer of zinc is applied for metallic when it comes to car marketplace and products which range from washing machines to DVD people. Llanwern invested £3.6m on its Zodiac line a few years ago. That is remaining open.
UNITED KINGDOM Business Minister Anna Soubry MP stated: "there is absolutely no doubt the metallic business is dealing with really challenging marketplace circumstances, with international overcapacity, high falls in costs and currency devaluations.
"but the government consistently work closely using industry to give help where we could."
Welsh Conservatives have actually labelled reports of huge work losses at Tata's website in Llanwern "surprising" and "devastating".