The internet search giant posted a statement on its official blog insisting that it had not joined a US government program called Prism.
The UK intelligence service GCHQ has also been accused of gathering intelligence on British citizens through the program, which is has been used by the US National Security Agency to access online communications.
Larry Page, Google's chief executive, and David Drummond, the company's chief legal officer, said that it had not given any government open access to information stored in their data centres, either directly or through a "back door".
They said: "We have not joined any program that would give the U.S. government or any other government direct access to our servers.
"Indeed, the U.S. government does not have direct access or a back door to the information stored in our data centres. We had not heard of a program called PRISM until yesterday.
"Any suggestion that Google is disclosing information about our users Internet activity on such a scale is completely false.
"We provide user data to governments only in accordance with the law. Our legal team reviews each and every request, and frequently pushes back when requests are overly broad or dont follow the correct process.
"Press reports that suggest that Google is providing open-ended access to our users data are false, period."
MPs from Britain's Intelligence and Security Committee are going to Washington next week to seek guarantees that US spies are not snooping on emails sent by British citizens.
Leaked US documents appeared to show that GCHQ, based in Cheltenham, has had access to the Prism system since 2010.
If true it raises the prospect that the agency has been able to circumvent UK restrictions on accessing people's communications by obtaining the information via the US authorities.
GCHQ is due to report to MPs next week to respond to the accusations, but it has already said that it operated to "a strict legal and policy framework".
Barack Obama, the US President, has also staunchly defended the surveillance of phone and internet activity by US spies, calling it a "modest encroachment" on privacy that was necessary to defend the United States from attack.
He said that Prism, which allowed NSA and FBI agents to tap into the servers of nine US internet giants including Facebook, Google, YouTube, Apple and others, was only used against specific individuals living abroad.
He said: "It does not apply to people living in the United States."
Several internet giants have now denied opening their servers up to the US government.
"We have never heard of Prism," said Apple spokesman Steve Dowling.
Facebook's chief security officer Joe Sullivan said the huge social network did not provide any access to government organisations.
The statement from Google, added: "We understand that the US and other governments need to take action to protect their citizens safety including sometimes by using surveillance.
"But the level of secrecy around the current legal procedures undermines the freedoms we all cherish."
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