The top Democrat on the House intelligence committee says Chairman Devin Nunes should recuse himself from heading the lawmakers’ investigation into Russia’s interference in the 2016 election and ties between the Trump campaign and the Kremlin.

Rep. Adam Schiff of California says Nunes should step away from the investigation because of a secret meeting he had with a source last week on the White House grounds.

After much consideration I believe Chairman should recuse himself from involvement in investigation/oversight of Trump campaign & transition pic.twitter.com/jpfA1x80Si — Adam Schiff (@RepAdamSchiff) March 27, 2017

Nunes said his source — whom he has yet to name — showed him intelligence reports in which the names of Trump associates had been shared among agencies after their communications were scooped up in U.S. surveillance of foreign officials.

Schiff says Nunes remains the only member of the House intelligence committee that has seen this information.