Microsoft, Google and other technology companies are asking the US Senate to muzzle the National Security Agency.

It comes two weeks after a bill passed to end the most controversial aspects of domestic spy programmes while stopping short of the technology industry's demands for greater restrictions on bulk collection of internet data. The Senate intelligence committee was due to meet yesterday to discuss the legislation.

The letter from the technology giants comes on the anniversary of the publication of documents exposing government surveillance tactics. The public backlash has prompted consideration of new parameters for spy programmes.