Google is facing growing opposition in Europe to its landmark US legal settlement with book publishers and authors, raising a fresh challenge to an agreement that could help determine the future structure of the digital books business.

While limited only to book rights in the US, the proposed settlement, which still needs court approval, has aroused consternation among European publishers, who fear they will lose some of their rights to millions of European works held in university libraries in the US, which have been drawn into Google’s ambitious book-scannning effort.