Washington (CNN) Sixty former CIA officials warned President Donald Trump in a statement on Friday that "the country will be weakened if there is a political litmus test applied before seasoned experts are allowed to share their views."

The letter, which comes after Trump's decision to revoke former CIA Director John Brennan's security clearance, was signed by former CIA officials who served under both Republican and Democratic administrations in positions such as analysts, senior analysts and officers.

It adds to a growing outcry against the President's recent action and comes after more than a dozen former senior intelligence officials denounced the move as "ill-considered" and "unprecedented" in a separate statement.

"All of us believe it is critical to protect classified information from unauthorized disclosure," reads the statement from the former CIA officials. "But we believe equally strongly that former government officials have the right to express their unclassified views on what they see as critical national security issues without fear of being punished for doing so."

The statement goes on to say, "Our signatures below do not necessarily mean that we concur with the opinions expressed by former Director Brennan or the way in which he expressed them. What they do represent, however, is our firm belief that the country will be weakened if there is a political litmus test applied before seasoned experts are allowed to share their views."

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