A former top counterterrorism official under Presidents Barack Obama and Donald Trump just torched the current administration’s plans to build a wall mainly to keep terrorists out of the United States.

In an article that appeared Tuesday on Just Security, a website about national security and the law, Nicholas Rasmussen decimated Trump’s argument for a border wall — and made it known he thought the president and others in the administration are lying about the extent of a crisis.

“There is no wave of terrorist operatives waiting to cross overland into the United States. It simply isn’t true,” he wrote. “Anyone in authority using this argument to bolster support for building the wall or any other physical barrier along the southern border is most likely guilty of fear mongering and willfully misleading the American people.”

That’s a huge statement for Rasmussen to make, and it directly contradicts repeated statements by Trump administration officials (and Trump himself), who have been trying to galvanize support for a wall on the nation’s southern border. Trump’s fight to get funding to build the wall has led to the weeks-long partial government shutdown.

On Monday night, for example, Homeland Security Secretary Kirstjen Nielsen tweeted, “The threat is real,” but wouldn’t offer any actual numbers of known terrorists trying to enter the US via the southern border. However, NBC News reported hours earlier that US law enforcement officials only detained six — yes, six — terrorists in the first half of 2018.

Though Rasmussen left his government post a year ago — he now works at the McCain Institute in Arizona — he’s still knowledgeable about the main terror threats to the United States. After all, it was his job to collect and analyze much of the intelligence in this sphere. And as he writes clearly in the piece, the idea that terrorists are streaming over the US-Mexico border simply isn’t right.

Individuals affiliated with terrorist groups like al-Qaeda or ISIS know that it’s harder to enter the US by coming over the border since 9/11, he says. So terrorist groups have a different game plan: compel people already in the United States to launch terrorist attacks. That, unfortunately, is what led to a 2015 terrorist attack in San Bernardino, California, that killed 14 people and a 2016 assault on a nightclub in Orlando, Florida, that left 49 people dead.

“For every dollar spent on a $5 billion southern border wall, American public safety could benefit exponentially more from spending it on counterterrorism elsewhere,” Rasmussen writes.

But he also points to another revealing factor: The administration has yet to show the public data that proves its case. If what the Trump administration is saying were true, “there would certainly be current intelligence assessments laying out the details of this threat, even citing specific cases of imprisoned terrorists that had made their way through the criminal justice system,” he wrote. None of that exists right now — at least not yet.

The former counterterrorism chief isn’t shy about criticizing the Trump administration. Heck, he even did it while he was in the Trump administration, albeit on the way out.

But that doesn’t make his writing any less serious. He knows what he’s talking about — and he’s saying the Trump administration doesn’t, and is lying to make its border wall case.