The biggest congressional critic of the National Security Agency’s bulk collection of US data hailed a White House review panel’s recommendations as a major victory for the privacy movement on Wednesday.

“Clearly, this report speaks to what I’ve heard not just from people here but around the world: that they know that liberty and security are not mutually exclusive,” said senator Ron Wyden, the Oregon Democrat on the Senate intelligence committee who has fought an uphill battle for years to reveal and stop what he considers overbroad and unnecessary surveillance.

“There are substantial, meaningful reforms in this,” Wyden said in an interview Wednesday evening with the Guardian.

In particular, Wyden hailed a finding of the review group, deep into its lengthy report, that undermined the NSA’s claim that the collection of all US phone records was indispensable for preventing terrorist attacks.

“Our review suggests that the information contributed to terrorist investigations by the use of section 215 telephony metadata was not essential to preventing attacks, and could readily have been obtained in a timely manner using conventional section 215 orders,” wrote the group, which is chaired by former CIA deputy director Michael Morrell.

Section 215 is a reference to the portion of the Patriot Act that the Obama administration and intelligence agencies cite to collect in bulk the phone records of millions of Americans and store them for five years. They argue it is a crucial tool to detect domestic connections to terrorism.

“Millions of Americans, having all these phone call records [collected] – who they call, when, a national human-relations database … these knowledgeable experts are saying it was not necessary,” said Wyden, who has accused the NSA and associated intelligence officials of misleading the public about the utility and necessity of the bulk phone records collection.

The review group proposed over 40 recommendations, including that the NSA’s phone records collection transition to control by a “private party,” such as a telecommunications firm. Several civil libertarian groups expressed wariness about the recommendation.

Wyden said he was still studying that and other aspects of the review. “Obviously, there’s going to be a lot of technical issues associated with telecoms having the information,” said Wyden. “That’s going to take some time to work through.”

But the review group’s public refutation of a central aspect of the case for bulk domestic phone data collection – disclosed first by the Guardian thanks to leaks from whistleblower Edward Snowden – comes just two days after a federal judge, Richard Leon, doubted from the federal bench that a program of what he considered dubious constitutionality has helped stop terrorism.

“The government does not cite a single case in which analysis of the NSA’s bulk metadata collection actually stopped an imminent terrorist attack,” Leon wrote in a Monday opinion that caused shockwaves in Washington.

For months, NSA officials and public advocates have insisted that the bulk collection is not surveillance at all – and that the real surveillance occurs only when the NSA sifts through the data. Yet the review group appeared to reject that perspective. “All intelligence reformers have felt strongly this data collection is not an inoffensive activity,” Wyden said. “It is digital surveillance.”

Wyden said he needed time to parse the full recommendations of the report. But he said that the report “certainly appears” to resolve another of his major concerns with the NSA: the authority for NSA to search its troves of foreign communications for Americans’ identifying information without warrants – which he calls the “backdoor search loophole” and also first disclosed by the Guardian. He also hailed the review group’s recommendation that a public advocate be placed on the secret surveillance panel known as the Fisa court so judges who sit in secret do not only hear from the government.

“This has been a big week for the cause of intelligence reforms,” Wyden said.

Wyden has been at the forefront of reform efforts. Years before Snowden leaked any data, Wyden –constrained by classification rules – warned that the government had secretly reinterpreted the Patriot Act to collect vastly more data on Americans than the law authorized. He succeeded in 2012 at making public the fact that the Fisa court had ruled on at least one occasion that NSA surveillance had violated the constitution.

And after months of private entreaties to clarify a public comment made by NSA director Keith Alexander in 2012, Wyden asked James Clapper, the director of national intelligence, if the NSA was collecting data on millions of Americans. Clapper untruthfully replied “not wittingly,” a comment for which the director has publicly apologized.

Not all privacy groups are as optimistic about the review group’s proposed reforms.

“Many of the recommendations do not go far enough, or raise other privacy concerns that must be fully assessed,” said Cynthia Wong of Human Rights Watch.

“For example, while the review group acknowledges the need to provide greater privacy protections to non-US persons, at the same time, the report ultimately leaves the door open to continued broad, indiscriminate surveillance of foreigners. This report should be viewed as a good start for what changes need in the end to be made.”

But the report’s assessment that the bulk collection had an inessential relationship with domestic counterterrorism provides a tailwind to a legislative effort supported by Wyden, the USA Freedom Act, to end it. That battle will resume in January, when Congress returns – and will find an early test when Obama announces which of the Review Group’s recommendations he will implement.

“I think this has been a big week for the cause of intelligence reforms,” Wyden said.