S&P forecast that auto sales on the continent would remain below 12 million this year, compared with almost 15 million in 2007, owing to Europe's poor economic state and concurrent drop in consumer confidence.
The 15 million auto level might be attained once again in 2018, the agency said in a study released on the sidelines of the Paris auto show.
Competitor Moody's downgraded the two major European auto manufacturers meanwhile, citing decreased demand and industrial problems.
Fiat and PSA Peugeot Citroen were both cut by one notch to "Ba3," with a negative outlook, a Moody's statement said.
The latest developments came against the background of the Paris auto show.