Britain's intelligence eavesdroppers GCHQ used the US' Prism programme but did not break the law in doing so, MPs and peers have concluded.
The secretive intelligence and security committee (ISC) said allegations that GCHQ had broken the law by gaining access to Prism, an internet surveillance scheme which whistleblower Edward Snowden revealed had been tapping private online communications since 2007, were "unfounded".
Its conclusion will trigger the usual round of whitewash accusations against the committee, which meets in private because it considers classified material.
"We have been quite explicitly and unapologetically concentrating on the question of illegality," chairman Sir Malcolm Rifkind told reporters in parliament.
A later probe will look at the content of the interceptions requested by GCHQ from American sources.
The committee's statement said it had scrutinised lists of the operations, British individuals and email addresses involved in all requests where GCHQ obtained intelligence from the US.
While confirming that the UK intelligence community had benefited from Prism, it said its work analysing the formal agreements regulating access to the material suggested no laws had been broken.
A minister signed the warrant for interception each time GCHQ sought information from the US, the statement confirmed.
It also warned that more work was needed to assess exactly how the legal framework governing the transfer of such operations works.
"Although we have concluded that GCHQ has not circumvented or attempted to circumvent UK law, it is proper to consider further whether the current statutory framework governing access to private communications remains adequate," the committee's statement noted.
"In some areas the legislation is expressed in general terms and more detailed policies and procedures have, rightly, been put in place around this work by GCHQ in order to ensure compliance with their statutory obligations under the Human Rights Act 1998.
MPs will now examine the "complex interaction" between the Intelligence Services Act, the Human Rights Act and the Regulation of Investigatory Powers Act to try and understand further the "policies and procedures that underpin them".
Foreign secretary William Hague said he had already written to committee chair Sir Malcolm Rifkind to thank him for his investigation.
"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 values," he said.
"The intelligence and security committee is a vital part of the strong framework of democratic accountability and oversight governing the use of secret intelligence in the UK.
"It will continue to have the full cooperation of the government and the security and intelligence agencies."
Rifkind told reporters he had not expected the paperwork required to get approval from Hague to be so substantial.
"I was surprised by the thoroughness and detail and how significant and substantial are the authorisation needed by the secretary of state," he commented.
"The amount of detail the agencies need to go into... is significantly more than was the case between 1995 and 1997, when I was the foreign secretary."