Unions at Opel/Vauxhall's Astra factory in the UK fear they may lose production of left-hand-drive models of the compact car to Germany.
Opel/Vauxhall's parent, PSA Group, will decide in the coming weeks which European factories will build the new-generation Astra, due in 2021, the German business paper Handelsblatt said.
The Astra is currently built in Ellesmere Port, northwest England, and Gliwice, Poland.
Opel's home plant of Ruesselsheim, near Frankfurt, could be picked to build left-hand-drive cars currently produced by Ellesmere Port, Handelsblatt said, quoting company sources.
The factory needs an extra model after production of the Zafira Tourer minivan runs out in the summer. Its only model then will be the Insignia midsize car.
The so-called "Site Selection Process" for the Astra has largely been completed, Handelsblatt said.
PSA is considering two options, the paper said:
1. Allocating 75% of Astra production to Ellesmere Port with the remaining volume produced in Ruesselsheim, instead of Gliwice.
2. Building 75% of Astras in Ruesselsheim, with Ellesmere Port producing only right-hand-drive versions for the UK, Ireland and South Africa.
There was no mention on whether Gliwice would get a new model to replace lost Astra output.
Option 2 is more likely because of Brexit and currency risks, Handelsblatt said. But the option depends on German unions agreeing to big job cuts at Ruesselsheim, which IG Metall is resisting.
A source at the Ellesmere Port factory told Automotive News Europe: "I believe it is a possibility depending on the Brexit outcome."
A Vauxhall spokesman said the company would not comment on speculation. "In general, we want to continue to improve the utilization of our plants and their performance. We are focusing on the production of profitable models," he said.
PSA CEO Carlos Tavares has previously said he was open to the idea of building right-hand-drive versions of PSA vehicles in Ellesmere Port to avoid tariffs between the UK and the EU in the event of a hard Brexit.
This could mean the factory gaining production of next-generation right-hand-drive Peugeot and Citroen cars alongside Astras as a hedge against Brexit.
Opel/Vauxhall has been shedding jobs under PSA CEO Carlos Tavares to restore the former General Motors business to long-term profitability.
The Astra was Opel/Vauxhall's second best-selling model in Europe last year after the Corsa subcompact hatchback. Astra sales fell 27% to 156,827 during the year, according to JATO Dynamics market researchers. Corsa sales dropped 7% to 214,324.