Vauxhall is axing 400 jobs making Astra hatch and sports tourer models at Ellesmere Port.
There are potentially 80 workers from Wales who could be affected when the shifts are reduced from two to one next year.
Owner PSA Peugeot Citroen said the rising cost of importing parts to make the cars affected their profits on each vehicle and with sales falling the cuts are necessary.
Traditional saloons, hatchbacks and estate cars have been replaced by SUVs and MPVs in families and businesses and this week Vauxhall is launching its new Grandland X SUV based on the PSA Peugeot 3008 and built on the same assembly lines in France.
After Vauxhall became part of PSA earlier this year the Ellesmere Port plant will have to compete for new models with its sister plants on the Continent making PSA and Opel models.
The next Astra is expected to share much of the platform and powertrain with the replacement for the Peugeot 308 which is expected to be built in France, and this will be tough for the UK operation.
PSA has also said it will delay making decisions on production centres until the outcome of Britain’s negotiations on leaving the EU and any level of trading tariffs are known.
Other car makers have pledged to continue making cars in the UK, notably Nissan and Honda.
The changing market for buying SUVs over hatchbacks will also affect UK production plans much sooner than the car makers intended or considered when they set down lines for new models a few years ago.
Britain’s engine plants have also been caught out by the move away from diesel and petrol models to hybrids and electric vehicles and the latter need far fewer moving parts so are easier and cheaper to build but raw materials for batteries offset these savings.