BRUSSELS, Dec 19 (Reuters) - The head of a pan-European carmakers association slammed a plan by the European Commission to cut carbon dioxide emissions from cars, saying it was unbalanced and level of fines was "totally unacceptable." "We are extremely disappointed with the process and disappointed with the content," Ivan Hodac, secretary-general of the European Automobile Manufacturers Association (ACEA) told Reuters shortly after the plan was announced on Wednesday.