Former FBI Director James Comey slammed President Trump and the Republican Party for doing "lasting damage" to the United States with their attacks on the FBI.

"How will Republicans explain this to their grandchildren?" Comey wrote on Twitter.

Malkin Slams 'Obnoxious' Claim by James Clapper: 'Spygate' Was About Bringing Down Trump

Mark Levin: Bombshell Revelations Show 'Mueller Probe Is Unconstitutional'

Comey's tweets came after Trump, his legal team and some of his supporters in Congress have intensified their attacks on the bureau following reports that an FBI informant had contacts with at least three members of Trump's presidential campaign.

Trump has claimed the informant was trying to damage him politically rather than protect the electoral process from foreign interference.

On "America's Newsroom," David Bossie said every American should be disturbed by the revelation that the FBI had a spy or spies inside the Trump campaign. He agreed with Trump that this could be "one of the biggest political scandals in history."

"And you have Democrats who hate this president more than they love this country," Bossie said, saying it's completely appropriate for Trump and Republican lawmakers to call for congressional oversight of the Russia investigation.

He noted that the probe has been going on for nearly two years -- with Special Counsel Robert Mueller leading it for the past year -- and it has yet to provide "one scintilla" of evidence of collusion between the Trump campaign and Russia.

Pavlich on FBI's Trump 'Informant': 'Obama Spied on Reporters, Why Wouldn't He Spy on a Campaign?'

Trump Shuts Down Question About Rosenstein at Appearance With South Korean President

Gohmert Calls for 2nd Special Counsel: Mueller Looking for 'Something to Take Trump Out'