Up to 200 jobs are to be axed at Jaguar's two Midland factories.
Workers at Castle Bromwich in Birmingham and the wood veneer centre at Browns Lane in Coventry were told of the redundancy programme by management on Friday.
The voluntary programme will apply to hourly paid workers – who mainly work on the production lines at both plants. The process has been described as part of an ongoing examination of the company, which has been fighting slumping sales.
A spokesman for Jaguar said: "This is part of our normal business to achieve higher overall efficiency improvements. This will help to adjust production volumes to match demand. There is no question of this being the end of Castle Bromwich.
"It is home to the new XF which is going into production later this year, and it is the home of the XK, one of the most popular cars we have produced."
Castle Bromwich, which employs 2,400 people, is expected to bear the brunt of the job losses, with 190 of the proposed 200 redundancies.
The plant, which saw a #200 million investment in an aluminium car body facility in 2003, is likely to see posts go on all the lines.
The XJ line is likely to be the main focus along with the XK line – which saw numbers increase last year as production was ramped up around its launch last May – is also likely to see some job losses as levels return to normal.
Around ten jobs are expected to be lost at the Browns Lane site, which continues to employ 500 people in the wood veneer centre after car production ended in 2005.
The spokesman said the redundancy was due to be completed by May, but would not be drawn on the levels of redundancy pay. But it is thought minimum payments are around #12,000 and rise depending on service and grading.
Dave Osborne, T&G national secretary for the car industry, said: "Since the closure of Browns Lane nearly two years ago, there has been a continual decline in sales, and despite the workforce repeatedly being told ‘you make ‘em, we’ll sell ‘em’, sales continue to slide.
"The workforce has lost confidence in the sales and marketing team and this announcement is another example of people losing their jobs due to the failures of management."
One Jaguar worker, who asked not to be named, said: "There are too many people at the plant for the number of cars the company is producing.
"But what about people's futures?"
Roger Maddison, national officer for trades union Amicus, which represents 1,000 of the 2,400 workers at Castle Bromwich, said: "We always knew that something like this would happen because the production quotas are down.
"They are only asking for volunteers and it is good news for the people who want to go and. It also means that Jaguar is not carrying people when production is quite low.
"There will also be a ramping up of production when the new S-Type starts later this year.
"This is sad in the short term, but we understand why the company is doing this and hopefully there will be a better future for Jaguar in the future."
Last year Jaguar sales slumped 12.01 per cent in the UK to 23,165 models, as the company chased a policy of focusing on its higher margin vehicles like the XJ and XK.
Jaguar reduced its continuing sales losses to just three per cent in January, thanks to the success of the XK sports car and the growing popularity of the diesel-powered variant of the range-topping XJ saloon, both of which it builds at Castle Bromwich.
Globally, sales of the XK were 155 per cent up at 12,000 vehicles last year, while the XJ was 15 per cent down at around 12,200 and S-Type 23 per cent down at 20,000.