Three hundred new jobs will be secured at Vauxhall's plant in Ellesmere Port, Cheshire, ahead of production of a new Astra model and second shift will be added at the Vivaro van facility in Luton, Bedfordshire, creating 250 jobs.
Vauxhall said the jobs marked the car giant's "first significant hire programme for a decade".
The announcement comes two years after the Ellesmere Port plant won a £125 million contract to build the next generation Astra.
Roger Maddison Unite national officer for the automotive sector said: "This is continued confirmation of the skills and expertise of the Vauxhall workforce and the world class vehicles they build. It demonstrates how companies like Vauxhall, working with Unite and the workforce, can secure jobs and skills for the future."
Tim Tozer, Vauxhall's chairman and managing director, said: "This is great news for Vauxhall and for British manufacturing.
"Both of our UK manufacturing plants have won long contracts with all-new products and as the business strengthens, we now need to take on more people to build these exciting new Vauxhalls."
The jobs will be phased in from the start of next year.