Enlarge Image YouTube screenshot by CNET / Common Cause

The latest figure with an opinion on the fight between Apple and the FBI is none other than NSA whistleblower Edward Snowden.

His conclusion? The FBI's claim that only Apple can bypass the security of the iPhone used by a terrorist is bogus.

"The FBI says Apple has the 'exclusive technical means' of getting into this phone," Snowden said Tuesday.

Snowden called the claim malarky, without using such a polite term. "Respectfully, that's bulls***," he said.

The former National Security Agency contractor, who fled the US and lives in Russia, made the remarks while speaking via a video link from Moscow at advocacy group Common Cause's conference in Washington DC.

Snowden is the latest voice to weigh in on the FBI's effort to force Apple into providing the agency with a backdoor to the iPhone's security, but his insight lends credence to the tech community's fears about compromising encryption. After exposing details of US and UK mass surveillance programs to the world, Snowden remains a controversial but an influential voice. Now, that voice is accusing the FBI of lying directly about its technical capabilities.

The FBI argues that the protections put in place by Apple cannot be overcome and that the iPhone 5C used by shooter Syed Farook is critical to its investigation of the December attack that left 14 people dead and another 22 wounded in San Bernardino, California.

Snowden followed up his comments by tweeting a link to a blog post from the American Civil Liberties Union that asserts the FBI is attempting to mislead the courts and the public about its ability to crack into the iPhone. In the post, ACLU technology fellow Daniel Kahn Gilmor calls the FBI's case against Apple a "power grab."

"The FBI wants us to think that this case is about a single phone, used by a terrorist," Gilmor said. In fact, it is an attempt "to weaken the ecosystem we all depend on for maintenance of our all-too-vulnerable devices" and to ensure that future software updates contain "deliberately weakened code."

The blog post also asserts that the FBI is misrepresenting the "auto-erase" feature it wants Apple to bypass and shows how the FBI could work around it.

The FBI's press office could not immediately be reached for comment. Apple did not respond to a request for comment.