Sources have informed the Allgemeine Zeitung the company's works council has paused the transition timeline.
Employee information sessions, which were due to be held this week, have been postponed indefinitely. Also delayed is the transfer of the bulk of GM's European operations to a new holding company named Opel Automobile GmbH.
Above: The new Opel Insignia, which will be sold in Australia as the next Holden Commodore, uses a GM platform.
At issue is Opel's International Technical Development Centre (ITEZ), which currently employs around 7700 people. The works council and the IG Metall union want to lock in future contracts for the development centre, including work that it will carry out on behalf of GM after Opel's sale to the PSA Group.
ITEZ is GM's second largest development centre and currently undertakes development not only for GM's European operations, but for projects throughout the world. It is reportedly deeply embedded within GM's powertrain division.
Automobil Woche estimates that in 2020 up to 30 per cent of ITEZ' work could still come from GM. If such a number is achieved, it could help stave off redundancies and cutbacks at Opel's white collar facility, with the PSA Group already employing around 13,000 people throughout its engineering department.
Above: The Opel Crossland X is based on a PSA Group platform.
This is the first major stumbling to appear after GM and the PSA Group announced the sale of Opel and Vauxhall in March.
Speaking to the trade publication, a spokeswoman for Opel's works council said there was no disagreement between PSA, GM and the works council. She noted, however, the discussions are complex, and figuring out all the details will take longer than expected.
Opel still hopes to have the deal completed during the second half of this year.