Jack Lew, who was Treasury secretary under former President Barack Obama, said Wednesday that the tax-cutting aspects of the House Republican health-care bill supported by the Trump administration are "reverse Robin Hood," robbing from the poor to reward the rich.

Working Americans who voted for Donald Trump for president may get "buyer's remorse if people actually look at the details of the tax policy" outlined in the GOP's health legislation that passed the House last week and went to the Senate, Lew said on "Squawk Box."

"People who earn more than $250,000 ... get a tax break [on capital gains] and you pay for it by cutting benefits that go to old people" and kids who are disabled, he said.

The Republicans' American Health Care Act as written would eliminate Obamacare taxes imposed on the wealthy that, in part, pay for health-care coverage for Americans.

The GOP measure calls for the repeal of a 3.8 percent investment tax, and a 0.9 percent Medicare payroll tax. Both of those apply to individuals earning $200,000 or more a year and couples earning more than $250,000.

On Monday, billionaire investor Warren Buffett told CNBC that the Republican health-care bill would "cut the hell out of taxes" for wealthy Americans like him.

The chairman and CEO of Berkshire Hathaway, who had supported Democrat Hillary Clinton for president, said his personal tax bill would be 17 percent lower under the GOP measure — or about $680,000 lower on a "little less than $4 million."

On the other side, billionaire real estate mogul Sam Zell told CNBC on Tuesday he disagrees with Buffett, saying that the GOP measure balances out the system by cutting taxes that should not have been imposed in the first place.

Zell, a former Democrat, said he's more of a Republican lately — conservative on fiscal matters but liberal on social issues.