A top Clinton-era labor economist is throwing cold water on the bid backed by Democratic presidential candidates Bernie Sanders and Hillary Clinton to boost the minimum wage to $15 an hour.

"Lately," blogged Brookings Institution fellow and Georgetown University professor Harry Holzer, "minimum wages have risen too high to $15 an hour in some cities."

Holzer, the chief Labor Department economist under former President Clinton, added that while the rise might work in a few cities, as a national policy "such increases are extremely risky."

Bernie Sanders wants the national minimum wage at $15. Hillary Clinton backed it for New York, but doesn't go as far as Sanders. AP Photo

With the issue of income inequality becoming a big part of the upcoming presidential election, there has been a fight over raising the rate from $7.25 to President Obama's preferred level of $10.10, endorsed by Holzer, even it it nicks job creation.

"In a Congressional Budget Office report last year, policy analysts predicted that Obama's proposal to raise the federal minimum wage to $10 an hour would raise wages for 16-24 million people while eliminating about half a million jobs — a reasonable tradeoff worth embracing, in my view," he wrote on the Brookings site.

But above that, as some cities like New York have endorsed, it can be a jobs killer.

"I have much more serious worries about a $15 an hour minimum wage, which constitutes a wage increase of 50 percent to 100 percent in most places (even after adjusting for inflation). In cities like Seattle, with a relatively more educated workforce and dynamic labor market, it might be a gamble worth taking. But in other cities, such as L.A. and Washington, D.C. — with their large populations of less-educated workers, including unskilled immigrants – such increases are extremely risky.

"In job markets where young or less-educated workers already have difficulty finding jobs and gaining important work experience, such mandates will likely make it much harder," he wrote.

Clinton recently endorsed New York's $15 minimum wage, though stopped short of making that the national wage.

"The national minimum wage is a floor, and it needs to be raised...but let's also remember that that cost of living is different," she said.

Sanders has proposed it for the national minimum wage.

Holzer's full blog is here.

Paul Bedard, the Washington Examiner's "Washington Secrets" columnist, can be contacted at pbedard@washingtonexaminer.com.