Harvard Law professor Alan Dershowitz warned Monday that special counsel Robert Mueller's decision to raid President Trump's personal lawyer's office is an assault on the privileged lawyer-client relationship.

Dershowitz said on Fox News that he believes the decision to raid Michael Cohen's office would be a sign that Mueller is trying to turn Cohen against Trump.

"This may be an attempt to squeeze Cohen," he said. "He's the lawyer, he's the guy who knows all the facts about Donald Trump, and to get him to turn against his client."

"This is a very dangerous day today for lawyer-client relations," he added.

Dershowitz, who has drawn the ire of Democrats for defending Trump, said Mueller's move is also dangerous because it gives the FBI the option of deciding what information seized from Cohen to pursue.

"I tell [clients] on my word of honor that what you tell me is sacrosanct," he said. "And now they say, just based on probable cause ... they can burst into the office, grab all the computers, and then give it to another FBI agent and say, 'You're the firewall. We want you now to read all these confidential communications, tell us which ones we can get and which ones we can't get.'"

"If this were Hillary Clinton being investigated and they went into her lawyer's office, the ACLU would be on every television station in America, jumping up and down," he added.

"The deafening silence from the ACLU and civil libertarians about the intrusion into the lawyer-client confidentiality is really appalling," Dershowitz said.

The famed law professor said Mueller's move will only convince more people not to cooperate and said he believes Mueller has "lost perspective" in the case.

Dershowitz recommended that Trump make a motion in court to take Cohen's materials away from the FBI and make a judge decide what evidence can be used and which cannot.