The documents, the latest in a series released by American intelligence leaker Edward Snowden, show that the Americans expected the UK’s GCHQ to work hard to meet their demands, The Guardian reported.

The papers reveal the close relationship between the GCHQ and its American counterpart the National Security Agency (NSA) but also raise fears that the US largest spying organization has immeasurable influence over the GCHQ.

In one document from 2010, GCHQ acknowledged that the US had "raised a number of issues with regards to meeting NSA's minimum expectations.” It said GCHQ "still remains short of the full NSA ask.”

Although British officials have rejected the GCHQ being subordinate to the NSA, the British spy agency itself has described UK’s surveillance laws and regulatory regime as a "selling point" for the Americans, according to the documents.

The papers also show that though Britain’s intelligence gathering has progressed immensely over the past five years nearly 60% of the UK’s Internet and phone intelligence comes from the NSA.

The UK's biggest fear is that "US perceptions of the … partnership diminish, leading to loss of access, and/or reduction in investment … to the UK,” according to the papers.

In one case, the NSA pays half of the costs of one Britain’s main eavesdropping programs in Cyprus.

A senior GCHQ manager in Cyprus said in November 2011 that lack of staff there would affect their commitment to the NSA.

"This is not sustainable if numbers reduce further and reflects badly on our commitments to the NSA."