WASHINGTON — Top House Democrats on Monday called on the Republican chairman of the House Intelligence Committee to recuse himself from the panel’s investigation into Russian meddling in the 2016 presidential election, thrusting the entire inquiry into jeopardy amid what they described as mounting evidence he was too close to President Trump to be impartial.

The demands followed revelations that the committee’s chairman, Representative Devin Nunes of California, had met on White House grounds with a source who showed him secret American intelligence reports. The reports, Mr. Nunes said last week, showed that Mr. Trump or his closest associates may have been “incidentally” swept up in foreign surveillance by American spy agencies.

The new revelation that the information actually came from a meeting held on the grounds of the White House intensified questions about what prompted Mr. Nunes to make the claim about the intelligence gathering, and who gave him the information.