The number of intelligence community officials who are blasting President Donald Trump for revoking former CIA Director John O. Brennan’s security clearance keeps going up.

And a key senator is drafting a legislative proposal to prevent a repeat.

A Thursday night statement denouncing Trump’s decision has so far featured the names of 15 former senior CIA and other intelligence agency leaders. And that’s been followed by another statement signed by 60 other former intelligence officials critical of the president’s move.

Among the signatories on the statement from the leaders are former Defense Secretary Robert Gates and retired Gen. David Petraeus, both of whom also led the CIA.

The group of 60 said in their statement that they might not all agree with Brennan’s political positions, but that it should be a separate issue from his eligibility for a clearance.

“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,” the former officials said. “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.”

In a separate bit of news, Virginia Sen. Mark Warner, the top Democrat on the Senate Intelligence Committee, announced Friday afternoon that he was drafting an amendment to the current two-bill spending legislation that would “block the President from punishing and intimidating his critics by arbitrarily revoking security clearances.”

Warner announced his amendment plan on Twitter, and an aide confirmed the intended vehicle is the appropriations bill that is currently the pending business on the Senate floor.

Watch: Trump Stands By Security Clearance Decision

Trump, speaking with reporters as he was leaving the White House earlier Friday, said he concurred with the view of Senate Intelligence Chairman Richard M. Burr on the question of Brennan’s statements.

The North Carolina Republican was critical of Brennan making statements to The New York Times about interactions between the president’s 2016 campaign operation and Russia.

“Director Brennan’s recent statements purport to know as fact that the Trump campaign colluded with a foreign power,” Burr said in a Thursday statement. “If Director Brennan’s statement is based on intelligence he received while still leading the CIA, why didn’t he include it in the Intelligence Community Assessment released in 2017? If his statement is based on intelligence he has seen since leaving office, it constitutes an intelligence breach. If he has some other personal knowledge of or evidence of collusion, it should be disclosed to the Special Counsel, not The New York Times.”

“Security clearances are very important to me, very, very important. and I’ve had a tremendous response for having done that,” Trump said Friday.

But the response from the group of former CIA directors and other national security officials was far from tremendous

 “We have never before seen the approval or removal of security clearances used as a political tool, as was done in this case. Beyond that, this action is quite clearly a signal to other former and current officials,” the former top officials said in their Thursday statement.  “As individuals who have cherished and helped preserve the right of Americans to free speech — even when that right has been used to criticize us — that signal is inappropriate and deeply regrettable.”