LONDON — A London-based advocacy group filed suit over America’s international data dragnet Monday, a complaint that one analyst said could have significant ramifications for US-British intelligence-sharing.
In a complaint filed with the Investigatory Powers Tribunal, Britain’s interception watchdog, Privacy International alleges that the National Security Agency and its British counterpart GCHQ are spying on one another’s citizens and swapping the intercepted information without proper oversight.
The complaint also accuses GCHQ of overstepping British law through the mass monitoring of UK communications.
‘‘It is a fundamental breach of the social contract if the government can operate with unrestrained power in such an arbitrary fashion,’’ said Eric King of Privacy International.
Privacy’s suit is one of several that have been spawned by NSA surveillance revelations.
In the United States, groups including the Electronic Privacy Information Center and the American Civil Liberties Union also are suing over the agency’s spying.
The Electronic Privacy Information Center on Monday filed an emergency petition with the Supreme Court asking it to review the NSA surveillance efforts. It said it took the extraordinary legal step of going directly to the highest court because the sweeping collection of Americans’ phone records has created “exceptional circumstances” that only the justices can address.
The group said it could not challenge the legality of the NSA program at the secret court that approved it, the Foreign Intelligence Surveillance Court, and because lower federal courts did not have jurisdiction over the secret court’s orders.
In Britain, the civil liberties group Liberty says it is finalizing its complaint before the Investigatory Powers Tribunal.
Over the past month, the NSA and GCHQ have seen details of their globe-spanning intelligence-gathering efforts splayed across the pages of the Guardian newspaper and other outlets
Some in Britain have expressed concerns that GCHQ is drawing on the NSA’s massive data pool to dodge restrictions on domestic espionage.
In its complaint, Privacy said it was concerned that its own communications had been intercepted by the Americans and subsequently handed to British authorities. It demanded an immediate end to GCHQ’s exploitation of NSA-obtained intelligence on British residents and an injunction against the blanket interception of UK data over fiber-optic cables.
GCHQ declined to comment on the suit. UK officials have insisted their spies work within the law.
Legal experts say Privacy’s complaint faces long odds at Britain’s Investigatory Powers Tribunal, where 10 out of more than 1,000 complaints have ever been upheld.
They’re divided as to its prospects, should it make its way to the European Court of Human Rights — a Strasbourg, France-based body whose rulings have occasionally frustrated UK leaders.
Former federal contractor Edward Snowden, who leaked the NSA documents, asserted in a video released Monday that the spy agency gathers all communications into and out of the United States for analysis.