A day after President Donald Trump alleged that then-President Barack Obama had ordered the wiretapping of the Republican's campaign headquarters, the White House says it won't comment further until congressional oversight committees investigate the matter.

In a statement, White House press secretary Sean Spicer cited unknown "reports" of "potentially politically motivated investigations" during the campaign, calling them "troubling."

"Reports concerning potentially politically motivated investigations immediately ahead of the 2016 election are very troubling," Spicer said. "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."

"Neither the White House nor the president will comment further until such oversight is conducted," he added.

Congressional investigators are probing Russian efforts to undermine the 2016 election as well as any contacts between Russian officials and the Trump campaign.

Early Saturday, Trump - apparently in response to reports by a conservative radio host and on the conservative website Breitbart - accused Obama of wiretapping Trump Tower and engaging in a "Nixon/Watergate" effort to undermine his presidency.

But a senior U.S. official said Saturday that there was no such wiretap. A spokesman for Obama also said that the former president never authorized a wiretap of Trump or any other American citizen.

Speaking on NBC News on Sunday morning, the former Director of National Intelligence James Clapper, who served in that post during the Obama administration, flatly denied that there was a wiretap authorized against Trump or his campaign during his tenure.

"There was no such wiretap activity mounted against the president elect at the time as a candidate or against his campaign," Clapper said on "Meet the Press."

He added that he would "absolutely" have been informed if the FBI had sought or received such a warrant to wiretap Trump or his campaign.

"I can deny it," Clapper continued.