Edward Snowden says the US National Security Agency is lying when it says it has no record of his emails to supervisors raising concerns about NSA surveillance programs, and that the release of one of his emails on Thursday proves it.

The NSA has long maintained that Snowden never voiced his concerns through proper channels before fleeing the US with a trove of secret documents, a position the agency reiterated on Thursday when it published what it claimed was the only email it could find from him.

That email contained a seemingly innocuous question about a legal matter and did not raise any specific objections to any NSA programs.

But in an interview with the Washington Post on Thursday, Snowden said that if the NSA can find one of his emails – after months of denying that its lawyers and higher-ups ever had any contact with him – then it must surely have the others he maintains he sent.

"Today's release is incomplete, and does not include my correspondence with the Signals Intelligence Directorate's Office of Compliance," Snowden said.

He added that in the latter correspondence, he was told that secret Presidential Executive Orders could take precedence over an act of Congress, directly contradicting the response from the NSA's Office of General Counsel that was published on Thursday.

In a televised interview with NBC's Brian Williams on Wednesday, Snowden said that he had also raised his concerns verbally with colleagues, management, and senior leadership at the NSA, but was warned that the agency would "destroy" him if he made waves.

On Thursday, he told the Post that it would "not take long" for NSA investigators to confirm that he'd had those talks, but said that internal policies and practices at the NSA are designed to suppress and ignore dissent.

"The fact that two powerful Democratic Senators – Ron Wyden and Mark Udall – knew of mass surveillance that they believed was abusive and felt constrained to do anything about it underscores how futile such internal action is – and will remain – until these processes are reformed," Snowden said.

Nonetheless, he said, he sees the NSA's decision to publish one of his emails as a step in the right direction.

"I'm glad they've shown they have access to records they claimed just a few months ago did not exist," he said, "and I hope we'll see the rest of them very soon ... Today's strangely tailored and incomplete leak only shows the NSA feels it has something to hide." ®