'Where is he getting this information?': ABC anchor grills Trump spokesperson over Obama wiretap allegations

ABC anchor Martha Raddatz grilled White House spokesperson Sarah Huckabee Sanders over President Donald Trump's largely unfounded allegation that former President Barack Obama personally directed law enforcement to look into the Trump campaign's ties to Russia.

The president suggested on Sunday that Congress include in its review of Russia's meddling in the US election reports that Obama's White House personally directed aspects of a corresponding law enforcement investigation of Russian meddling in the 2016 election.

In an exchange on "This Week" on Sunday, Raddatz said Trump was making "extremely serious charges" and confronted Sanders about Trump's sources, asking, "Where is he getting this information?"

Sanders said outlets like the BBC previously reported that federal investigators sought warrants to monitor Russian banks suspected of potentially steering money to the Trump campaign — though the report did not include Trump's wiretapping allegation.

"The bigger thing is — let's find out. Let's have an investigation. If they're going to investigate Russia ties, let's include this as part of it. And so that's what we're asking," Sanders said.

RELATED: President Trump accuses Obama on Twitter of wiretapping him

Throughout the interview, Raddatz repeatedly sought answers to the many questions inspired by Trump's tweets, which offered no supporting evidence for their claim.

The ABC anchor first asked if Trump was motivated to tweet about Obama after reading a pieceabout the subject in the far-right website Breitbart. Raddatz pointed out that although Breitbart cites the New York Times as a source, the report "doesn't say anything definitive."

"There is nothing equivocating about what he says. 'I just found out that Obama had my wires tapped.' That's not 'Look into something.' He says it happened," Raddatz said.

When Raddatz said the reports cited by Breitbart included anonymous sources — a reporting practice Trump has repeatedly decried — Sanders dismissed the point, instead claiming that if the reports were true, the wiretaps would be the "greatest overreach and the greatest abuse of power that I think we have ever seen and a huge attack on democracy itself."

The ABC anchor repeatedly attempted to understand the legal steps necessary for federal investigators to bug Trump's phone.

"If there was an order, there would have to be probable cause shown before it was granted, evidence of wrongdoing. So, isn't the president saying this indeed happen confirming that the investigation had enough evidence to get a FISA order?" Raddatz asked.

"I'm not sure if they can create wrongdoing. They've been trying to make the case for it. The FBI says that this is BS, the House intelligence chair has said that there is no evidence of it. But I don't know that that would indicate that intelligence services wouldn't have attempted to see if there was something at that point in October," Sanders replied.

Raddatz then said that if the claim was true, Trump may have been disclosing classified information.

"A FISA court order wiretap is highly classified information. Why is it acceptable for the president to tweet something like that out?" Raddatz asked.

"I don't think he's tweeting out classified information. He's talking about could this have happened? Did this happen?" Sanders replied.

As the conversation appeared to wind down, Raddatz pressed yet again to present clear evidence that proved Obama wiretapped Trump.

"You keep saying, if, if, if. The president of the United States said it was a fact. He didn't say I read a story in Breitbart or 'The New York Times' or wherever else. He said, just found out that Obama had my wires tapped in Trump Tower. That's not an if," Raddatz said.

"I will let the president speak for himself," Sanders replied.

"You're his spokesperson," Raddatz said

"And I'm speaking about it right now," Sanders said.

"But you're backing off of it. You're backing off of it," Raddatz said.

The interview came just minutes after Trump called for a congressional investigation into whether Obama overstepped his authority investigating Russia's involvement in the 2016 election.

On Saturday, Obama spokesman Kevin Lewis denied the previous White House interfered in the investigation into the 2016 election.

"A cardinal rule of the Obama administration was that no White House official ever interfered with any independent investigation led by the Department of Justice. As part of that practice, neither President Obama nor any White House official ever ordered surveillance on any US citizen. Any suggestion otherwise is simply false," Lewis said.

Watch the exchange below, via ABC: