The California Air Resources Board (CARB) said VW’s proposals did “not adequately address overall impacts on vehicle performance, emissions and safety”.
The CARB also said the proposed fix was not fast enough.
It said it would continue its investigation as well as talks with VW to find a suitable solution.
The head of the CARB, Mary Nichols, said: “Volkswagen made a decision to cheat on emissions tests and then tried to cover it up.
“They continued and compounded the lie and when they were caught they tried to deny it. The result is thousands of tons of nitrogen oxide that have harmed the health of Californians. They need to make it right.”
The federal Environmental Protection Agency (EPA) also said the VW plan for cars with 2 liter diesel engines was not acceptable.
The rejection comes ahead of a meeting between VW CEO Matthias Muller and EPA chief Gina McCarthy on January 13 to discuss the emissions scandal.
Volkswagen said in response: “Today’s announcement addresses the initial recall plans Volkswagen submitted to CARB in December. We are committed to working co-operatively with CARB and other regulators, and we plan to continue our discussions tomorrow when we meet with the EPA.”
The issue affects almost 600,000 cars in the United States and up to 11 million worldwide.
The scandal has severely damaged VW’s reputation and sparked investigations in several countries.
In the US alone VW is facing fines that could run into tens of billions of dollars.
The Department of Justice is suing Volkswagen on behalf of the EPA with a lawsuit that was filed on January 4 in a federal court in Detroit, Michigan.
The DoJ said the filing was the first step in “bringing Volkswagen to justice”.
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