Republican Rep. Ryan Costello Ryan Anthony CostellloTrump struggles to stay on script, frustrating GOP again Bottom line Former GOP Rep. Costello launches lobbying shop MORE (R-Pa.) on Friday called on the White House to fire special assistant Kelly Sadler over her derisive remarks about Sen. John McCain John Sidney McCainCindy McCain endorses Biden: He's only candidate 'who stands up for our values' Biden says Cindy McCain will endorse him Biden's six best bets in 2016 Trump states MORE (R-Ariz.).

"I think the White House should apologize and fire her. I think the remarks are disgusting. It's depressing, Craig, when you hear that kind of talk when you look at the service of Sen. McCain," Costello told CBS News host Craig Melvin.

"As a party, I think we need to do a better job of getting out in front of this stuff quickly, condemning it, and saying it has no place in our discourse," Costello added.

Echoing similar comments from former Vice President Joe Biden Joe BidenOmar fires back at Trump over rally remarks: 'This is my country' Trump mocks Biden appearance, mask use ahead of first debate Trump attacks Omar for criticizing US: 'How did you do where you came from?' MORE, Costello said mocking a dying senator represented a degradation in America's political discourse.

During a closed-door meeting on Thursday, The Hill reported, Sadler dismissed McCain's opposition to President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE's CIA director pick, Gina Haspel, stating “It doesn’t matter, he’s dying anyway.”

Sources familiar with the matter told The Hill that they believed the comment was meant as a joke, though it did not go over well with White House communications staffers present at the meeting.

McCain, 81, was diagnosed last year with an aggressive form of brain cancer, which he is receiving treatment for at his home in Arizona.

The White House is facing mounting scrutiny over its refusal to acknowledge the incident, drawing criticism from lawmakers on both sides of the aisle and members of the media.

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During Friday's daily press briefing, White House press secretary Sarah Huckabee Sanders refused to address the matter, dodging questions about Sadler's comments.

“I'm not going to validate a leak, one way or another, out of an internal staff meeting," Sanders said at the briefing.

Sadler, reportedly, has since apologized to the senator's daughter, Meghan McCain, who has also called for Sadler to be fired.

Meghan McCain, who co-hosts "The View," said Friday she couldn't understand an environment in which an aide could make such a comment and then "could come to work the next day and still have a job."