"What the President said was just patently false, and the wrecking ball it created now has banged into our British allies and our German allies," Schiff said on NBC News' "Meet the Press."
He said that Trump "needs to put an end" to growing damage resulting from his claims.
"I suspect what's really at root here, Chuck, is this is just how the President does business. Now maybe this is the way he conducted his real estate business, with half-truths and sometimes no truths and a lot of bluster," Schiff said. "That, in my opinion, is no way to run a business, but it's an even worse way to run a country."
He said that Trump's allegations are "dangerous" to the United States and are "already alienating allies."
"I have a lot of respect for Susan Collins, but I have to differ with her on this," Schiff said, referring to Sen. Susan Collins (R-ME). "She said we need to get to the bottom of this. We are at the bottom. There is nothing at the bottom."
"Will Director Comey say that definitively tomorrow, do you expect?" Chuck Todd asked.
"I expect that he will, and I hope we can put an end to this wild goose chase," Schiff replied.
— Meet the Press (@MeetThePress) March 19, 2017
White House press secretary Sean Spicer on Thursday cited a claim by Fox News commentator Andrew Napolitano that British spy agency GCHQ eavesdropped on Trump on Obama’s behalf.
GCHQ issued on Friday an angry denial of Napolitano's “utterly ridiculous” allegation. Trump's administration reportedly extended a formal apology to the British government and promised not to repeat the claim again.
Spicer later said that Trump's administration had no “regret” about sparking the international incident.
On Friday, Trump suggested that he and a visibly uncomfortable German Chancellor Angela Merkel were both bugged by the Obama administration.