A leaked document jolted the European Union capital of Brussels in October, laying out in painstaking detail plans by Google to undermine new legislation that could severely damage its digital advertising business.

"Academic allies” would raise questions about the new rules. Google would attempt to erode support within the European Commission to complicate the policymaking process. And the company would try to seed a trans-Atlantic trade dispute by enlisting U.S. officials against the European policy, according to a copy reviewed by The New York Times and confirmed by Google.

For many officials in Brussels, the document confirmed what they had long suspected: Google and other American tech giants are engaged in a lobbying campaign to stop stronger regulation against them.