The NSA whistleblower Edward Snowden has condemned the new surveillance bill being pushed through the UK's parliament this week, expressing concern about the speed at which it is being done, lack of public debate, fear-mongering and what he described as increased powers of intrusion.

In an exclusive interview with the Guardian in Moscow, Snowden said it was very unusual for a public body to pass an emergency law such as this in circumstances other than a time of total war. "I mean we don't have bombs falling. We don't have U-boats in the harbour."

Suddenly it is a priority, he said, after the government had ignored it for an entire year. "It defies belief."

He found the urgency with which the British government was moving extraordinary and said it mirrored a similar move in the US in 2007 when the Bush administration was forced to introduce legislation, the Protect America Act, citing the same concerns about terrorist threats and the NSA losing cooperation from telecom and internet companies.

"I mean the NSA could have written this draft," he said. "They passed it under the same sort of emergency justification. They said we would be at risk. They said companies will no longer cooperate with us. We're losing valuable intelligence that puts the nation at risk."

His comments chime with British civil liberties groups who, having had time to read the small print, are growing increasingly sceptical about government claims last week that the bill is a stop-gap that will not increase the powers of the surveillance agencies.

David Cameron, searching for cross-party support, assured the Liberal Democrats and Labour that there would be no extension of the powers.

But internal Home Office papers seen by the Guardian appear to confirm that there would be an expansion of powers. Campaigners argue that the bill contains new and unprecedented powers for the UK to require overseas companies to comply with interception warrants and communications data acquisition requests and build interception capabilities into their products and infrastructure.

The interview with Snowden, in a city centre hotel, lasted seven hours. One of only a handful of interviews since he sought asylum in Russia a year ago, it was wide-ranging, from the impact of the global debate he unleashed on surveillance and privacy to fresh insights into life inside the NSA. The full interview will be published later this week.

Edward Snowden with a framed piece of a computer that was destroyed in the Guardian basement at the request of the British government. Photograph: Alan Rusbridger

His year-long asylum is due to expire on 31 July but is almost certain to be extended. Even in the unlikely event of a political decision to send him to the US, he would be entitled to a year-long appeal process.

During the interview, Snowden was taken aback on learning about the speed at which the British government is moving on new legislation and described it as "a significant change". He questioned why it was doing so now, more than a year after his initial revelations about the scale of government surveillance in the US, the UK and elsewhere around the world, a year in which the government had been largely silent.

He also questioned why there had been a move in the aftermath of a ruling by the European court of justice in April that declared some of the existing surveillance measures were invalid.

He said the government was asking for these "new authorities immediately without any debate, just taking their word for it, despite the fact that these exact same authorities were just declared unlawful by the European court of justice".

He added: "Is it really going to be so costly for us to take a few days to debate where the line should be drawn about the authority and what really serves the public interest?

"If these surveillance authorities are so interested, so invasive, the courts are actually saying they violate fundamental rights, do we really want to authorise them on a new, increased and more intrusive scale without any public debate?"

He said there had been government silence for the last year since he had exposed the scale of surveillance by the NSA and its British partner GCHQ. "And yet suddenly we're told there's a brand new bill that looks like it was written by the National Security Agency that has to be passed in the same manner that a surveillance bill in the United States was passed in 2007, and it has to happen now. And we don't have time to debate it, despite the fact that this was not a priority, this was not an issue that needed to be discussed at all, for an entire year. It defies belief."

It is questionable how much impact his comments will have on parliamentarians, even though he is an expert witness, with inside knowledge of the surveillance agencies.

Snowden has become a champion for privacy campaigners. But, though his revelations prompted inquiries by two parliamentary committees, he has won little vocal support among parliamentarians.

The Conservatives deny there is any need for a debate on surveillance versus privacy. Labour and Liberal Democrats have been hesitant too about joining the debate, fearful of a backlash in the event of a terrorist attack.

Even backbench MPs who think the intelligence agencies have a case to answer hold back from public expressions of support for a whistleblower sought by the US government.

The British government is justifying the proposed new legislation on the grounds not only of the European court ruling but of US intelligence fears of a terrorist attack, in particular concerns of an attempt to blow up a transatlantic airliner said to be emanating from an alleged al-Qaida bombmaker in Yemen linked to hardline Islamist groups in Syria and Iraq.

Snowden said the Bush administration had used the threat of another terrorist attack on America after 9/11 to push through the Protect America Act. The bill had to be brought in after the New York Times disclosed the surveillance agencies had been secretly engaged in wiretapping without a warrant.

Snowden said: "So what's extraordinary about this law being passed in the UK is that it very closely mirrors the Protect America Act 2007 that was passed in the United States at the request of the National Security Agency, after the warrantless wire-tapping programme, which was unlawful and unconstitutional, was revealed."

He said the bill was introduced into Congress on 1 August 2007 and signed into law on 5 August without any substantial open public debate. A year later it was renewed and the new version was even worse, he said, granting immunity to all the companies that had been breaking the law for the previous decade.