Japanese car giant Honda is to cut production at its UK factory from three shifts to two, threatening 340 jobs.
Most cars built at the plant in Swindon, Wiltshire, are exported and sales in other countries have not been as strong as in the UK.
"Over the last 12 months, we haven't seen the growth we'd anticipated. With no increase forecast for the next couple of years, we must scale our manufacturing activity accordingly," said Ian Howells, senior vice president of Honda Motor Europe.
"However, with the restructuring we're taking today, and our new model plans, we remain confident in the long-term future of our Swindon plant."
"Our Swindon operation continues to be the hub for our European car manufacturing activity," he added.
Honda said it will enter into consultation on a proposal to reduce the workforce by 340 production employees.
As well as moving to two shifts, production will be consolidated on to one line, to "improve production flexibility and efficiency" while production volumes continue at the current level.
Honda has been manufacturing cars at Swindon since 1992 and currently builds the Civic, Civic Tourer, CR-V and Jazz models for the UK and European markets.