Republican Rep. Ryan CostelloRyan Anthony CostellloOvernight Energy: Park Service closing Joshua Tree after shutdown damage | Dems deliver trash from parks to White House | Dems offer bills to block offshore drilling | Oil lobby worries about Trump trade fight Ex-GOP Rep. Ryan Costello joins group pushing carbon tax Exiting lawmakers jockey for K Street perch MORE (R-Pa.) on Friday called on the White House to fire special assistant Kelly Sadler over her derisive remarks about Sen. John McCainJohn Sidney McCainMellman: Where are good faith and integrity? GOP senator says Republicans didn't control Senate when they held majority Pence met with silence after mentioning Trump in Munich speech 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 BidenJoseph (Joe) Robinette BidenHarry Reid says he won’t make 2020 endorsement until after Nevada caucus Hillary Clinton met with Biden, Klobuchar to talk 2020: report The Hill's Morning Report - What to watch for as Mueller’s probe winds down 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 TrumpDonald John TrumpSchiff urges GOP colleagues to share private concerns about Trump publicly US-China trade talks draw criticism for lack of women in pictures Overnight Defense: Trump to leave 200 troops in Syria | Trump, Kim plan one-on-one meeting | Pentagon asks DHS to justify moving funds for border wall 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."