Volkswagen AG, BMW AG and Daimler AG-owned Mercedes-Benz have halted sales of some of their plug-in hybrid cars in Europe in the wake of new emissions regulations, Automotive News reported on Thursday.

The new Worldwide Harmonized Light Duty Vehicles Test Procedure (WLTP) regime, which went into effect on Sept. 1, gives higher CO2 readings than the old New European Driving Cycle (NEDC) system, pushing vehicles into a higher tax bracket.

The new rules could take away tax incentives offered to cars with ultra-low emissions in certain countries, the Automotive News report said, according to Reuters. Automakers have to decide whether the extra cost to fit a bigger battery is worth the incentives given, according to the report.

The introduction of WLTP has forced some carmakers to withhold non-conforming models from showrooms, prompting them to discount other models to defend their market share.

In other news, the German government is on track to find a solution for tackling pollution from diesel vehicles but there is no agreement yet, a government source said after Chancellor Angela Merkel chaired a meeting on Friday in Berlin. Final details of a deal that seeks to avert bans on older vehicles from city streets should be hammered out when leaders of Merkel’s coalition of conservatives and center-left social democrats meet on Monday.