Documents obtained by the Guardian shed light on the National Security Agency’s (NSA) access, a programme the government calls PRISM.
The 41-slide PowerPoint presentation is classified top secret and was used to train intelligence agents in the “collection directly from the servers” of major US service providers.
In a statement, Google said: “Google cares deeply about the security of our users' data. We disclose user data to government in accordance with the law, and we review all such requests carefully.
“From time to time, people allege that we have created a government 'back door' into our systems, but Google does not have a back door for the government to access private user data."
It was also revealed this week the US government had ordered major network operator Verizon to hand over all of its records of US customers.
Those records are just call logs, but the PRISM programme also includes the contents of communications which has greater implications on privacy.