In demanding that Congress open an investigation, the White House on Sunday doubled down on its unsubstantiated allegation that former President Barack Obama abused his executive authority to tap current President Donald Trump's telephone during the 2016 campaign.

Congress and the FBI are already investigating whether Russia influenced the campaign to help Trump get elected and now the president has called on Congress to investigate whether his phone was tapped.

Trump offered no evidence to substantiate his seemingly wild accusation, which has been categorically rejected by an Obama spokesperson as well as Democrats and also called into question by some Republicans.

Republican Senator Marco Rubio, who sits on the Senate Intelligence Committee, said the White House "will have to answer as to what exactly" Trump was referring to when he claimed Obama had Trump Tower wiretapped during the election.

Lawmakers from both parties are asking the White House for evidence to substantiate the allegation as presidents don't have the power to order the surveillance of private citizens.

The latest denial of any impropriety came from Obama's director of national intelligence. James Clapper said no such wiretap activity was carried out against Trump as a candidate or against his campaign.

"Absolutely, I can deny it," Clapper said during a national TV interview. He left the White House when Trump took office on January 20.

But White House Press Secretary Sean Spicer pressed ahead, calling on Congress to probe "very troubling" reports "concerning potentially politically motivated investigations immediately ahead of the 2016 election." Spicer did not respond to inquiries about citing those reports.

Listening in on Trump Tower

Trump said the wiretapping happened in October at Trump Tower, the New York skyscraper where he ran his campaign and transition. It's also where he lived before taking office.

"President Donald J. Trump is requesting that as part of their investigation into Russian activity, the congressional intelligence committees exercise their oversight authority to determine whether executive branch investigative powers were abused in 2016," Spicer said.

Critics have slammed the allegations as nothing more than a smear campaign intended to divert public attention from investigations into Moscow's alleged connections to the Trump campaign.

Josh Earnest, who was Obama's press secretary, said 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, in a series of tweets Saturday, in an attempt to distract from the attention being given to campaign-season contacts by his aides with a Russian official, including campaign adviser Jeff Sessions before he resigned from the Senate to become attorney general.

Both the FBI and Congress are investigating those contacts.

"There is one page in the Trump White House crisis management playbook, and that is simply to tweet or say something outrageous to distract from a scandal," Earnest said. "And the bigger the scandal, the more outrageous the tweet."

bik/sms (AP, Reuters, AFP, dpa)