WEST PALM BEACH, Fla. >> The White House said today that Congress should expand its investigation of Russian meddling in the 2016 election to include President Donald Trump’s unverified allegation that former President Barack Obama stepped over the legal line in the campaign.

While Trump claimed, without evidence in a series of tweets Saturday, that his predecessor had tapped the telephones at Trump Tower, Obama’s director of national intelligence said no such action was carried out against the New York businessman as a candidate or against his campaign.

“Absolutely, I can deny it,” said James Clapper, who left his job when Trump took office Jan. 20.

An Obama spokesman has said Trump’s accusation was “simply false.” Lawmakers from both parties appealed for Trump to provide proof for the startling claim, yet the White House said there would be no further comment until “such oversight is conducted” by the congressional intelligence committees.

“It’s called a wrap-up smear. You make up something. Then you have the press write about it. And then you say, everybody is writing about this charge. It’s a tool of an authoritarian,” said House Democratic leader Nancy Pelosi.

White House press secretary Sean Spicer announced the request for a congressional inquiry in a statement that referred to “very troubling” reports “concerning potentially politically motivated investigations immediately ahead of the 2016 election.”

He did not elaborate or respond to inquiries about those reports.

Trump said the wiretapping happened in October at the New York skyscraper where he ran his campaign and transition.

Spicer said the White House wants the committee to “exercise their oversight authority to determine whether executive branch investigative powers were abused in 2016.”

Spicer’s chief deputy, Sarah Huckabee Sanders, said she thinks Trump is “going off of information that he’s seen that has led him to believe that this is a very real potential.”

Josh Earnest, who was Obama’s press secretary, said presidents do not have authority to unilaterally order the wiretapping of American citizens, as Trump has alleged was done to him. FBI investigators and Justice Department officials must seek a federal judge’s approval to investigate by demonstrating that probable cause exists.

Earnest accused Trump of leveling the allegations to distract from the attention being given to campaign-season contacts by Trump aides with a Russian official, including campaign adviser Jeff Sessions before he resigned from the Senate to become attorney general. The FBI is investigating those contacts, as is Congress.

Rep. Devin Nunes, chairman of the House Intelligence Committee, said in a statement that the committee “will make inquiries into whether the government was conducting surveillance activities on any political party’s campaign officials or surrogates.”

The committee’s top Democrat, Rep. Adam Schiff of California, said Trump was following “a deeply disturbing pattern of distraction, distortion and downright fabrication.”

Sen. Tom Cotton, R-Ark., a member of the Senate Intelligence Committee, said he had seen no evidence to back Trump’s allegations, but was sure the committee would include the matter in its Russia investigation.

The office of House Speaker Paul Ryan, R-Wis., referred questions to Nunes, while a spokesman for Senate Majority Leader Mitch McConnell, R-Ky., said McConnell would not tell the Senate committee how to do its work.

Trump’s call for Congress to investigate Obama has risks, though, particularly if damaging information about him or his associates is uncovered. Lawmakers are promising to follow the evidence wherever it takes them.

In his tweets, Trump compared the alleged wiretapping to “Nixon/Watergate” and “McCarthyism!” And he called Obama a “Bad (or sick) guy.”

Trump said in the tweets that he had “just found out” the information, though it was unclear whether he was referring to a briefing, a conversation or a media report. The president in the past has tweeted about unsubstantiated and provocative reports he reads on blogs or conservative websites.

The tweets stand out, given the gravity of the charge and the strikingly personal attack on the former president. Trump spoke as recently as last month about how much he likes Obama and how much they get along, despite their differences.

“How low has President Obama gone to tapp my phones during the very sacred election process. This is Nixon/Watergate. Bad (or sick) guy!” he tweeted, misspelling ‘tap.’

Obama spokesman Kevin Lewis said Saturday that a “cardinal rule” of the Obama administration was that no White House official ever interfered in Justice Department investigations, which are supposed to be conducted free of political influence.

Lewis said neither Obama nor any White House official had ever ordered surveillance on any U.S. citizen. “Any suggestion otherwise is simply false,” Lewis said.

Trump has been trailed for months by questions about his campaign’s ties to Russia. Compounding the situation is the U.S. intelligence agencies’ assessment that Russia interfered with the election to help Trump triumph over Hillary Clinton, along with disclosures about his aides’ contacts with a Russian official.

Clapper appeared on NBC’s “Meet the Press,” Sanders and Earnest were on ABC’s “This Week,” Pelosi was on CNN’s “State of the Union,” and Cotton was on “Fox News Sunday.”