Allegations that British spy agency GCHQ illegally tapped global internet traffic and phone calls, which it shared with its US counterpart, the National Security Agency (NSA), are "unfounded", according to Parliament's Intelligence and Security Committee (ISC).
Only last week, the ISC said it would investigate the allegations, after former NSA contractor and whistleblower, Edward Snowden, had accused the US and UK spy agencies of snooping on phone calls and internet usage.
If this were true, it would be a "matter of various serious concern" and "would constitute a serious violation of the rights of UK citizens", the ISC said.
In the past week, though, it says that it has now taken what it deems detailed evidence from GCHQ.
It said its snap investigation involved looking into GCHQ's access to content of communications, the legal framework that governs that access, and the arrangements GCHQ had with its overseas counterparts for sharing such information.
"From the evidence we have seen, we have concluded that [the allegations] are unfounded," the ISC's statement said.
The ISC said it received "substantive reports" from GCHQ, including a list of counter-terrorist operations for which GCHQ was able to obtain intelligence from the US in any relevant area, a list of all of the UK-based individuals tasked with monitoring such arrangements, a list of the warrants and internal authorisations that were in place for each of these individuals being targeted, and a number of the intelligence reports that were produced as a result of this activity.
It also received reports of formal agreements that regulated access to this material.
"We discussed the programme with the NSA and our congressional counterparts during our recent visit to the United States. We have also taken oral evidence from the director of GCHQ [Sir Iain Lobban] and questioned him in detail," the ISC said.
The committee said it was also satisfied that the US conformed with GCHQ's statutory duties, and in each case where GCHQ sought information from the US, a warrant for interception, signed by a government minister, was already in place.
It concluded that GCHQ had not circumvented or attempted to circumvent UK law.
The ISC said its next step is to "consider further whether the current statutory framework governing access to private communications remains adequate".
It will examine how the Intelligence Services Act, the Humans Rights Act and the Regulation of Investigatory Powers Act currently interact, something that the Interception of Communications Commissioner is also considering.
Foreign Secretary William Hague has welcomed the ISC's findings.
"I see daily evidence of the integrity and high standards of the men and women of GCHQ. The ISC's findings are further testament to their professionalism and value," he said..
"I have written to Sir Malcolm Rifkind to thank him for the Committee's prompt and thorough investigation," he added.