The chairman of the House intelligence committee, Republican Devin Nunes, told reporters on Wednesday that US spies may have swept up information on Donald Trump "inadvertently" during the president's transition period. 

The comments prompted the intelligence committee's ranking Democrat, Alan Schiff, to accuse his opposite number of acting on behalf of the White House, instead of behaving impartially.  

Read: US Congress hearings on Russia could descend into a partisan slugfest

Citing anonymous sources, Nunes - who was himself part of the Trump transition team - said Trump and his associates may have been "monitored" as part of an "incidental collection." He added that the revelation did not bolster Trump's unproven assertion that he was wiretapped at the behest of outgoing President Barack Obama.

'Somewhat' vindicated

Trump - potentially in hot water for his tweets accusing Obama and spy agencies of collusion that would have been illegal - welcomed Nunes' comments, saying he felt "somewhat" vindicated.

"I very much appreciated the fact that they found what they found," Trump said.

For Democrat Schiff, however, the comments created "profound doubt" about the efficacy of the investigation being carried out. In particular, he lamented the way that Nunes - as committee chairman - had shared the information with the president and media before the committee itself had been consulted.

"This is not how you conduct an investigation," Schiff told a news conference. "You don't take information that the committee hasn't seen and present it orally to the press and to the White House before the committee has a chance to vet whether it's even significant."

Chairman or patsy?

In comments to the news organization CNN, Schiff said Nunes needed to decide "whether he is the chairman of an independent investigation... or he's going to act as a surrogate of the White House, because he cannot do both."

The brief of the committee is to investigate potential Russian influence on the 2016 presidential race. It began before Trump took office on January 20.

Read: Constant information drip deepens Donald Trump's Russian woes

Lines of questioning from Republican and Democratic committee members appeared to diverge during Monday's questioning of security officials. While Democrats concentrated on unmasking Russian officials allegedly in contact with the Trump team, Republicans wanted to hear about the importance of identifying and prosecuting those responsible for intelligence leaks.

Trump's claims about the Obama wiretap led the administration to claim the spying had been conducted not by the FBI or National Security Agency, but by Britain's GCHQ surveillance agency. The claim was vehemently denied by Britain.

rc/jr (AFP, AP, Reuters)