SAN FRANCISCO — In a major legal setback for Google, a federal appeals court here said on Tuesday that a lawsuit accusing the Internet giant of illegal wiretapping could proceed.

The ruling, which comes at a moment when online privacy is being hotly debated, has its origins in a much-publicized Google initiative, Street View, which tried to map the inhabited world.

In addition to photographs, Street View vehicles secretly collected e-mail, passwords, images and other personal information from unencrypted home computer networks.

The scooping of data brought outrage and investigations in at least a dozen countries when it was first revealed in Germany in 2010. It also prompted a handful of lawsuits by United States citizens who said Google had violated their privacy and was illegally wiretapping them. Those suits were condensed into one case, which was heard by a California court.