The Washington Post reported yesterday that the internet giant had turned to the NSA, which conducts surveillance and codebreaking for the federal government, in the wake of a cyber attack it believes came from China.

The agency is responsible for securing the US administration's computer networks against similar breaches, and is said to be helping Google to understand and analyse the attacks.

Sources say that the agreement will not allow the NSA to view users' searches or access email accounts, but the deal has angered some members of the online community.

The Electronic Privacy Information Centre, a public research centre based in Washington, has filed a freedom of information request seeking details of the agency's relationship with Google.

"Google and NSA are entering into a secret agreement that could impact the privacy of millions of users of Google's products and services around the world," the centre's executive director Marc Rotenberg told the New York Times.

Sam Diaz, blogger and senior editor at ZDNet, a technology website, said he felt "squeamish" about the possibility of information sharing between Google and the government, and was sceptical about the NSA's ability to help protect the company's infrastructure.

"I mean no disrespect to my country or my government but I have to ask: Is Washington really the best choice if you're looking for help with something as serious as cyber security?" he wrote.