Daimler shares tumbled 3.7percent in morning trading on the Frankfurt Stock Market, while Volkswagen stock was marked down 2.9percent and by 2.5percent for BMW shares, as the carmakers faced up to the threat of a wave of lawsuits.
The weekly news magazine Der Spiegel reported last week that the carmakers, which also included VW’s luxury offshoots Porsche and Audi, have been consulting with each other since the 1990s over their vehicles, costs, suppliers and the handling of diesel emissions.
The report comes in the wake of the diesel emissions scandal that rocked the German car industry and hit confidence in the nation’s car business. VW admitted in September 2015 to cheating on pollution tests on more than 11million vehicles around the world.
The car industry is one of the heavyweights of the German manufacturing sector, directly employing more than 800000 people, and last year generating sales totalling 405billion (R5.98trillion).
BMW insisted that it does not manipulate emissions tests and that it complies with legal requirements, saying it was “a matter of principle” for the premium carmaker.
Both Daimler, the manufacturer of luxury Mercedes-Benz vehicles, and VW have described the cartel reports as speculation.
On Friday German Transport Minister Andreas Scheuer threatened to fine carmaker Daimler 3.75bn over a diesel emissions scandal, Der Spiegel magazine reported.
The report comes after Scheuer last week questioned Daimler boss Dieter Zetsche in a closed-door meeting over how many Mercedes-Benz vans and cars need to be fixed after a regulator found illegal software in one of its models.
Spiegel, citing no sources, said Scheuer expressed concerns that a total of 750000 Mercedes-Benz vehicles could be affected, and that the ministry could impose fines of up to 5000 a car.
A spokesperson for the transport ministry said that the carmaker and the transport ministry had agreed to clear up highly complex technical issues related to diesel emissions.
Last month, Daimler was ordered by motor vehicle authority Kraftfahrt-Bundesamt (KBA) to recall Vito vans fitted with 1.6litre diesel engines because it said they breached emissions rules.
Daimler has said it would appeal against KBA’s decision to classify its software as illegal and contest the findings in court if necessary, although it said it was co-operating fully.
Der Spiegel said that there was considerable evidence that diesel engines of the Mercedes C-Class models were also affected and that Daimler representatives would be summoned to the ministry, ahead of a planned follow-up meeting of Zetsche and Scheuer later this month.
The report said at least a further 80000 vehicles might have to be recalled as a result.
A spokesperson for Daimler said the group had committed to keeping the nature of its discussions with the Transport Ministry confidential and would not comment.