Nunes' remarks were made near the beginning of a testimony from the acting U.S. director of national intelligence on a whistleblower complaint about efforts by Trump to solicit the Ukraine government's help to investigate Democratic presidential hopeful Joe Biden whose son worked in Ukraine.
The House Intelligence Committee earlier on Thursday released the complaint.
The Trump administration had initially argued it was not covered by a whistleblower statute that would require its automatic disclosure to Congress.
The administration dropped its opposition to its release after a political firestorm erupted over news reports of some of the details in the complaint.
While a formal impeachment inquiry announced on Tuesday by House Speaker Nancy Pelosi is led by Democrats, some of Trump's fellow Republicans joined them in calling on the administration to send the report to Congress.