A former ambassador and White House ethics czar called on President Donald Trump to release his tax returns as the Russia scandal widens.

Norman Eisen, who served as former President Barack Obama's ethics lawyer and U.S. ambassador to the Czech Republic, argued Friday morning on CNN that there was ample evidence to pursue perjury charges against Attorney General Jeff Sessions over his role in the scandal.

"He can face perjury charges," Eisen told "New Day." "When you watch that video ... I see a categorical declaration. I think he's exposed, (and) I think that's why we need a special counsel."

Eisen, now a governance studies fellow at the Brookings Institute, said a full and independent investigation was needed to probe the ties between the Trump campaign and Russia.

"Issue after issue -- it has that Watergate feel to it," Eisen said. "It all leads me back to (the) Watergate question: Follow the money."

He reminded anchor Alisyn Camerota that Donald Trump Jr. had boasted in 2008 that "Russians make up a pretty disproportionate cross-section of a lot of our assets," and Eisen wants to know how closely the president's money is tied to Russian oligarchs.

"We need to see those Trump tax returns," Eisen said. "That's where this is headed."