British spies have had access to some of the information extracted and stored from SMS messages by the NSA, the Guardian newspaper said in revelations based on files leaked by former NSA contractor Snowden.
The spy programme, codenamed Dishfire, collects "pretty much everything it can", rather than merely storing communications of existing surveillance targets, according to a joint investigation by the daily and Channel 4 News.
Through the vast database, which was in use as late as 2012, the NSA gained information on those who were not specifically targeted or under suspicion, the report said.
The latest revelations state that the NSA's British counterpart, GCHQ, had searched NSA's database for information regarding people in the UK.
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The NSA, however, told the BBC that its programme only stored "lawfully collected SMS data". It added: "The implication that NSA's collection is arbitrary and unconstrained is false."
The latest revelations came a day before US President Barack Obama is to make a speech proposing curbs to NSA surveillance programmes exposed by Snowden. The changes will be based partly on a review of NSA activities by a White House panel.
Snowden has been charged with espionage in the US and is currently a fugitive in Russia, where he has been granted temporary asylum.