WASHINGTON — The United States National Security Agency (NSA) is authorised to spy on citizens of the country’s closest allies, including Britain, even though the English-speaking countries have long had an official non-spying pact, according to a newly disclosed memorandum.

The classified NSA document, which appears to be a draft and is dated January 2005, states that under specific circumstances, the intelligence agency may spy on citizens of Britain without that country’s consent or knowledge. Provided by former NSA contractor Edward Snowden, the memo is labelled secret and “NOFORN”, indicating that it may not be shared with any foreign country.

In recent months, the agency’s activities have stoked anger across the world after leaked documents exposed American spying on various foreign leaders. But, until now, there has been almost nothing disclosed about spying among the “Five Eyes” countries — the US and its close intelligence partners Britain, Canada, Australia and New Zealand.

The NSA declined to respond to questions on whether the draft became official policy and whether spying on Britain without its consent had ever taken place. In a written reply to questions, it said: “NSA works with a number of partners and allies in meeting its foreign intelligence mission goals and, in every case, those operations comply with US law and with the applicable laws under which those partners and allies operate.”

Referring to an intelligence-sharing compact struck in March 1946, the memo said the two nations had agreed “both governments will not target each other’s citizens/persons”.

That agreement, however, came with a caveat that “when it is in the best interest of each nation”, unilateral spying by one nation on the other could take place.

It also expands that mandate to allow spying by the US on any of the “Five Eyes” countries. THE NEW YORK TIMES