In a speech on Thursday, FBI director James Comey invoked "national security and public safety" to push for more permissive government surveillance policies, claiming new encryption technologies are poised to leave law enforcement agencies "in the dark" as they try to hunt down terrorists and child molesters.

Civil liberties watchdogs criticized Comey's claims, saying that the encryption tools would have no bearing on police and FBI operations, and that privacy is a federally guaranteed right.

Laura W. Murphy, director of the Washington Legislative Office of the American Civil Liberties Union, said Comey "is wrong in asserting that law enforcement cannot do its job while respecting Americans’ privacy rights. In fact, federal law explicitly protects the right of companies to add encryption with no backdoors."

Comey rejected that argument, claiming that agents in "law enforcement, national security, and public safety are looking for security that enhances liberty."

As cell phone users become more concerned over their right to privacy, particularly in the wake of NSA whistleblower Edward Snowden’s revelations, technology companies like Apple and Google are starting to offer elemental protection tools on phones and other software. But allowing users to lock their mobile devices and refusing to hand over private data, Comey said, could make it harder for FBI agents to do their jobs.

"Those charged with protecting our people aren’t always able to access the evidence we need to prosecute crime and prevent terrorism even with lawful authority," Comey said in a speech at the Brookings Institute. "We have the legal authority to intercept and access communications and information pursuant to court order, but we often lack the technical ability to do so."

Comey said that citizens should allow the government extensive access to their private information and trust that law enforcement agents will use it "pursuant to the rule of law, with clear guidance and strict oversight." He said the best way to do that may be expanding the Communications Assistance for Law Enforcement Act (CALEA), a bill passed in 1994 that requires telecommunications companies to build surveillance capabilities into their equipment and services.

Twenty years is "a lifetime in Internet age," Comey said.

Apple and Google say their encryption tools—released in response to public outcry after recent leaks exposed warrantless government surveillance against U.S. citizens—would allow users to lock their phones permanently, preventing both law enforcement agencies and the technology companies themselves from breaking into their devices.

But Comey, who outlined several scenarios in which police used cell phone data to track down and later convict a variety of criminals—from drug kingpins to abusive parents—called those tools an advertising ploy that could stymie justice at every turn.

"Encryption isn’t just a technical feature; it’s a marketing pitch," Comey said. "It’s the equivalent of a closet that can’t be opened. A safe that can’t be cracked. And my question is, at what cost?"

After Comey’s speech, a Google spokesperson told ABC News that its upcoming products, which will roll out with the encryption software pre-installed, will provide "added security" to users "while giving law enforcement appropriate access when presented with a warrant."

"Encryption is simply the 21st century method of protecting personal documents," Google said in a statement. "[And] while we won't be able to provide encryption keys to unlock phone data directly, there are still a number of avenues to obtain data through legal channels."

Electronic Privacy Information Center (EPIC) said Comey's comments were "surprising" and "disturbing."

Moreover, the encryption would not prevent agents from obtaining information through real-time wiretaps or data that is stored elsewhere, such as emails, and in some cases, old text messages.

But Comey said that internet and cell phone users had become paranoid after revelations that exposed the invasive surveillance tactics taken on by the NSA and other agencies. He said he was concerned that suspicion of law enforcement could lead to a nightmare scenario for innocent people when the FBI is thwarted in national security efforts because of encryption technology.

"Perhaps it's time to suggest that the post-Snowden pendulum has swung too far in one direction—in a direction of fear and mistrust," Comey said. "There will come a day—and it comes every day in this business—where it will matter a great deal to innocent people that we in law enforcement can't access certain types of data or information, even with legal authorization. We have to have these discussions now."

While Comey said encryption tools could aid criminals seeking to evade law enforcement, the ACLU pointed out that allowing additional government surveillance carries similar risks. "Whether the FBI calls it a front door or a backdoor, any effort by the FBI to weaken encryption leaves our highly personal information and our business information vulnerable to hacking by foreign governments and criminals," Murphy said.