Suzuki's Vitara and Fiat Chrysler's Jeep Grand Cherokee diesel models both violate emissions rules and must be fixed or face a ban on sales across Europe, the Dutch road authority RDW ruled on Thursday.

Acting as the reference regulator for the European Union, the RDW said it had found both the Jeep Grand Cherokee and Vitara had used "prohibited emissions strategies" that led them to emit higher levels of harmful nitrogen oxide on the road than under testing conditions.

The authority said Jeep had developed a software fix and that the authority had ordered the company to recall the model across Europe to roll it out.

It added that Suzuki had yet to find a credible solution for the Vitara.

"Suzuki must come with adequate improvement measures or the RDW will begin the process of revoking its European type approval," the RDW said in a statement, adding that it had also started the process of revoking approval for the Jeep Grand Cherokee as a "precautionary measure."

Regulators across the world have been testing diesel models since Volkswagen admitted in 2015 that it used illegal software to cheat U.S. emissions tests.

Dutch State Secretary for Infrastructure Stientje van Veldhoven said in a letter to parliament she would inform prosecutors of the RDW's findings.

Fiat Chrysler and Suzuki could not immediately be reached for comment.