LONDON, United Kingdom — The United States has been relying on the UK and its surveillance-friendly laws to spy on its behalf, possibly including work prohibited under US law, according to the latest story from the Guardian newspaper’s ongoing investigation of documents leaked by whistleblower Edward Snowden.

In exchange, the documents say, the US paid the UK’s top spy agency $150 million over the last three years.

It’s a relationship embraced and encouraged by GCHQ (Government Communications Headquarters), the UK's equivalent of the US National Security Agency. In addition to the money, the UK also drew heavily upon the intelligence gathered by the NSA. Some 60 percent of the UK’s high-value intelligence was either collected directly by the NSA or derived from its work, the leaked papers say.

As a result, the UK government has worked hard to keep that relationship intact.

“Our key partnership is with the US,” one UK government dossier noted. “GCHQ must pull its weight and be seen to pull its weight.”

By 2013, another GCHQ memo said, the UK should have “exploited to the full our unique selling points of geography, partnerships [and] the UK's legal regime.”

"We both accept and accommodate NSA's different way of working," that memo said. "We are less constrained by NSA's concerns about compliance."

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For example, one review noted, the UK lent "unique contributions" to the US investigation into Faisal Shahzad, an American citizen living in the US when he attempted to bomb New York's Times Square in May 2010.

The nature of GCHQ’s assistance is not further explained. US law, however, prohibits NSA surveillance of its own citizens.

The story exposed more details on the extent of data-harvesting operations in the UK, where spy officials said their goal is to "exploit any phone, anywhere, any time.”

The UK is researching how to pull personal data from mobile phone apps, the Guardian revealed. There has been a 7,000 percent increase in the amount of personal information available to GCHQ in the last five years.

The revelations came from a trove of documents leaked to the Guardian by former NSA contractor Edward Snowden.

Snowden, who left the US in May in advance of the disclosure, was granted one year’s temporary asylum in Russia on Thursday, allowing him to leave Moscow’s Sheremetyevo International Airport for the first time since he arrived there on June 23.