Sean Spicer. getty White House press secretary Sean Spicer and NBC's Peter Alexander had an intense back-and-forth during Monday's press briefing.

Alexander's line of questioning homed in on President Donald Trump's credibility, after Spicer relayed a quote from Trump about the positive February jobs report at Friday's press briefing. Trump had told Spicer that the reports "may have been phony in the past, but it's very real now."

Trump said on the campaign trail and after his election that jobs reports were "phony" and "totally fiction."

"You spoke on behalf of the president, quoting him on the jobs report on Friday," Alexander said. "You said, 'They may have been phony in the past, but it's very real now.'"

"They are very real now," Spicer cut in.

"The question is: When should Americans trust the president?" Alexander said. "Is it phony or real when he says that President Obama was wiretapping?"

Trump set the political world ablaze when he tweeted earlier this month, without evidence, that Obama had illegally ordered wiretaps on Trump Tower phones during the election. Neither Trump nor the White House has provided evidence to back up his claims.

"He doesn't really think that President Obama went up and tapped his phone personally," Spicer said.

"He suggested that," Alexander shot back.

"But I think there's no question that the Obama administration, that there were actions about surveillance and other activities that occurred in the 2016 election," Spicer said. "That is a widely reported activity that occurred back then. The president used the word 'wiretap' in quotes to mean, broadly, surveillance and other activities."

Spicer claimed that "many news outlets" reported this during the election and that the same outlets were now asking for proof from Trump. However, no outlets had reported that Obama ordered the wiretapping of Trump's or his campaign aides' phones.

Alexander moved on to the Congressional Budget Office's score for the American Health Care Act — the House Republicans' plan to replace the Affordable Care Act, more commonly known as Obamacare. The NBC reporter asked if Trump viewed past CBO reports as real but now thought they were phony as they related to the healthcare plan he hopes to pass through Congress.

Spicer said the CBO projection for the ACA was wildly off in terms of how many additional people it said would be insured under the landmark healthcare law.

"So the only point, Peter, is to make sure that people understand if you're looking to get a bull's-eye, accurate prediction as to where it's going, the CBO was off by more than half last time," he said. "This is not about what my understanding or my belief of the CBO is. The last time they did this, they were wildly off, and the number keeps declining."

"I guess the question is: When can we trust the president when he says something is phony and when he says it's real?" Alexander responded, and the exchange started to become somewhat testy.

"Hold on, hold on. You asked a question about the CBO, and now you're conflating it with a question about the president?" Spicer said.

"When he says something, can we trust that it's real?" Alexander asked.

"Yes!" Spicer cut in.

"—or should we assume that it's phony?" Alexander said over Spicer. "Well ... "

"But you just said it's real?" Spicer said.

"How can we believe that it's real when you told us it was phony then but now it's real?" Alexander said. "The president said the numbers were phony then but they are very real now. So how can we trust anything he says that he won't later say, 'Actually, it was the opposite'?"

Spicer said the statement about the jobs report centered on the unemployment rate, which fluctuates based on which calculation is used to determine it. Going back to the CBO report, Spicer said, "That's not a question of our credibility; it's a question of theirs."

Alexander then tried to ask his question in the shortest form he could.

"Can you say affirmatively that whenever the president says something, we can trust it to be real?" he said.

"If he's not joking, of course!" Spicer shot back, to which Alexander asked, "How do we know he's joking?"

Spicer's response: When Trump "speaks authoritatively," he's speaking "as the president of the United States."

The exchange wrapped up with Alexander asking whether Trump believes that 3 million to 5 million people voted illegally in the 2016 presidential election, as Trump has claimed, or if he was just joking.

"He does believe it!" Spicer said.

Watch the clip:

