A comedian and ex-Celebrity Apprentice staffer who claims to have worked with Donald Trump for six years has made shocking new accusations against the US President.

Noel Casler allegedly worked in talent logistics on the set of Celebrity Apprentice while Trump was host, and also worked on his Miss Teen Universe pageants.

In a stand-up show this month, Casler accused Trump of recreational drug use and said he acted inappropriately towards teenage beauty pageant contestants.

"I worked on a bunch of those beauty pageants he had in the '90s, too. That was a good idea, Miss Teen Universe? Yeah, that's like giving Jeffrey Dahmer a cooking show," he said.

"He would line up the girls on the side of the stage, and he would inspect them. Literally, he would stick his little freaking doll fingers in their mouth and look at their teeth."

"I'm not kidding, this is true, he would line them up like they were pieces of meat. He'd be like, 'You, you, and you, if you want to win I'm in the penthouse suite, come and see me.'"

Casler said he had signed a 24-page nondisclosure agreement but that he felt compelled to break it.

"I didn't know then he was becoming president. Now, it's 'no way dumbass.' I'm telling you everything I know," he said.

He also called the President a "speed freak" and said he took the attention deficit hyperactivity disorder drug Adderall to help him read cue cards while filming Celebrity Apprentice.

"He can't read, so he gets really nervous," Casler said.

"So he gets nervous and he crushes up these pills. That's why he's sniffing when you see him in debates, and when you see him reading.

"That's why he's tweeting. He's out of his mind. It makes sense if you think about it.

"Methamphetamine was invented by the Nazis to keep the fighter pilots up all night on bombing runs.

"So it makes sense that Trump would use it to hate-tweet in his self-centred rage at 4am on the toilet."

This guy worked on Celebrity Apprentice for 6 years. He did the after parties & was Jared & Ivanka’s handler. Donald Trump abused Adderall on the set & it made him crazy. He even snorted Adderall. Mark Burnett knew it. It’s scary watch tape: https://t.co/EhGQTOI8Vr

— Tom Arnold (@TomArnold) December 13, 2018

Casler's comments later prompted actor and comedian Tom Arnold to also come forward regarding Trump's alleged drug use.

"Donald Trump abused Adderall on the set & it made him crazy. He even snorted Adderall. Mark Burnett knew it. It's scary," he wrote in a tweet.

Actress and vocal Trump critic Kathy Griffin also weighed into the saga, throwing her support behind Casler and vouching for his credibility.

I've known @CaslerNoel for years. He has always been super professional and discreet. I'm so glad he's decided to reveal this important information about Trump. Thank you Noel, I know this isn't easy. pic.twitter.com/iZF5P9njMe

— Kathy Griffin (@kathygriffin) December 14, 2018

"I've known @CaslerNoel for years. He has always been super professional and discreet. I'm so glad he's decided to reveal this important information about Trump. Thank you Noel, I know this isn't easy," she posted on social media.

The White House has not responded to the claims.

The fresh claims come in the midst of yet another White House scandal sparked by the resignation of Interior Secretary Ryan Zinke — the fourth Cabinet member to leave under an ethical cloud.