(CNN) — Former FBI Director James Comey pushed back on President Donald Trump’s spying claims on Wednesday, warning that attacking the FBI “will do lasting damage to our country.”

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In a tweet that did not address the President by name, the former FBI director wrote, “Facts matter. The FBI’s use of Confidential Human Sources (the actual term) is tightly regulated and essential to protecting the country. Attacks on the FBI and lying about its work will do lasting damage to our country. How will Republicans explain this to their grandchildren?”

In a second tweet on Wednesday, Comey called on the American public to “seek truth.”

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The comments from Comey, who was abruptly fired by the President last year, come after Trump questioned whether the FBI placed “spies” in his campaign.

Multiple outlets reported last week that a confidential source working for the FBI spoke with several Trump campaign aides. US officials have told CNN, however, that a confidential intelligence source was not planted inside the campaign to provide information.

The Justice Department has asked its inspector general to determine whether there was any wrongdoing in the FBI’s handling of its Russian interference counterintelligence investigation.

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