Vauxhall plans to slash a further 250 jobs at its Ellesmere Port factory, adding to the 400 staff cuts announced in October.
The car manufacturer wants to boost productivity at the Cheshire-based plant by moving to a single production shift from April this year.
Vauxhall, which was bought by Peugeot-owner PSA Group in £1.9 billion deal in 2017, told staff on Monday morning following a meeting with union Unite on January 4.
In a statement, Vauxhall said it was committed to Astra production at Ellesmere Port and would conduct 45-day consultation with workers.
It added: "At a meeting held on Thursday 4 January 2018 between representatives from Vauxhall Motors and UNITE the Union, the company explained that although the initial voluntary separation programme at its Ellesmere Port plant announced in October (aligned to adjustment of production volumes in order to protect its future) has been successful, it needs to initiate a further voluntary programme for eligible employees of a further 250 heads in the period from April to the end of September 2018."
Around 1,900 staff manufacture the Vauxhall Astra at Ellesmere Port and a further 1,400 people produce the Vauxhall Vivaro van in Luton.
The workforce at Ellesmere Port will fall to 1,200 once the job cuts are complete.
Justin Madders, Labour MP Ellesmere Port & Neston, said it was more "devastating news" for workers in the area.
He added: "When previous job losses were announced in October, it was made clear that manufacturing costs were higher at Ellesmere Port than some other plants.
"That is why I called on the government to urgently intervene and work with the management to reduce costs and improve productivity, for example by creating incentives to encourage suppliers to relocate to Ellesmere Port.
"Sadly, and unlike on previous occasions when the facility has faced difficulties, ministers have provided warm words but no concrete action, while governments in other countries are pulling out all the stops to improve competitiveness."
PSA, which owns Peugeot and Citroen, agreed to buy the loss-making European arm of General Motors (GM) in March.
The move aimed to secure GM's exit from the UK and Europe while transforming PSA into Europe's second-largest car maker.
However, the takeover sparked concern in the UK about the impact on thousands of jobs at Vauxhall plants and supply companies.