Howard Stern said on Wednesday that Donald Trump’s proposed border is a giant waste of money and was simply cooked up as a campaign tool that “morons can get behind.”

Stern ripped the controversial wall on his SiriusXM radio program a day after Trump delivered a prime-time address from the Oval Office touting what he called the need for a barrier separating the United States and Mexico.

“The wall’s a problem because it’s a waste of money, even Donald knows that,” said Stern — who goes back decades with Trump, hosting the then-real estate mogul on his show numerous times before his White House bid.

“You gotta know Donald a bit to understand what’s going on here. The wall’s a simplistic answer to our problems with immigration. It’s something that, you know, morons can get behind because they’re like, ‘Oh yeah, if you build a wall no one can get over it.’ But it’s not that simple,” Stern told listeners of his eponymous show.

Stern blasted Trump’s demand of $5.7 billion in funding for the border wall — which Democrats have repeatedly rejected — saying the price tag wouldn’t cover the costs of such an expansive undertaking.

“You’re talking about building a massive wall across this country on the southern border. It’s a tremendous amount of property and a tremendous amount of area to cover,” said Stern. “You’re not going to get a whole wall for $5 billion. If you really want a wall, it’s probably going to cost you some trillions of dollars.”

Trump, Stern exclaimed, should “be straight up with people.”

“I would love to see Donald come on last night and go, ‘F— this, I’m not going to bullshit you guys. I want $20 billion.”

Howard Stern has described himself as a friend of Donald Trump, having hosted Trump on his terrestrial radio show a number of times when Trump was a real estate magnate and fixture of the gossip circuit in New York City. Egged on by Stern, Trump spoke openly about his sex life and delivered some sharp criticism of anyone he saw as an enemy. But Stern said that he now sharply disagrees with Trump’s politics, and hasn’t been shy to let the president know it.