The European Union's top court on Tuesday ruled that a key transatlantic data sharing deal relied on by companies such as Facebook was invalid in the light of spying revelations in the Edward Snowden scandal, AFP reports.

In a major blow to US tech firms, the court said the 2000 "Safe Harbour" agreement between the United States and the EU did not sufficiently guarantee the protection of Europeans' personal data and must be struck out. The stunning decision stems from a David-and-Goliath complaint against social media giant Facebook lodged against Irish authorities by Max Schrems, an Austrian law student privacy campaigner.

"The Court of Justice declares that the (European) Commission’s US Safe Harbour Decision is invalid," the European Court of Justice in Luxembourg said in its three-page judgment.