The drop in earnings for men is the biggest challenge facing the economy, according to Stephen Moore, the man President Donald Trump has said he wants to nominate to the Federal Reserve board.

Speaking Tuesday with CNBC's "Squawk Box," Moore faced questions about past writings, some of which have been classified as sexist by his detractors. Anchor Becky Quick asked him specifically about a piece he wrote for National Review in which he worried about a society where women earned more than men.

"The biggest problem I see in the economy over the last 25 years is what has happened to male earnings, for black males and white males as well," Moore said. "They've been declining. That is, I think, a big problem."

"I want everybody's wages to rise, of course. People are talking about women's earnings. They've risen," he added.

Since 2010, real median weekly earnings for men have risen about 2.1 percent, according to the Bureau of Labor Statistics. Women's real earnings have gone up 3.9 percent during the period.

"The problem actually has been the steady decline in male earnings, and I think we should pay attention to that, because I think that has very negative consequences for the economy and for society," he said.