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White House chief of staff Jack Lew refused to call the individual mandate for health care a tax, continually referring to it as a "penalty" or "charge," despite the Supreme Court's ruling that it should be considered a tax.

"The Supreme Court looked at what the structure of the law was and they saw that one percent of the people would be paying this charge if they chose not to avail themselves of health insurance," Lew told me this morning on "This Week." "For that one percent who have chosen not to buy health insurance, and just to pass the burden on to others, there's this penalty."

On Thursday, the Supreme Court ruled that the cornerstone of President Obama's health care legislation, the individual mandate, was indeed constitutional on the grounds that it acts as a tax.

Chief Justice John Roberts sided with the Supreme Court's four liberal members in the majority opinion, writing that "The Affordable Care Act's requirement that certain individuals pay a financial penalty for not obtaining health insurance may reasonably characterized as a tax. Because the Constitution permits such a tax, it is not our role to forbid it, or to pass upon its wisdom or fairness."

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But in my interview this morning on "This Week," Lew refused to acknowledge that it was a tax, saying, "The law set it up as a penalty for the people who make that choice. The court found it constitutional. Frankly what you call it is not the issue."

I pressed Lew on the penalty vs. tax issue, which was the center of Roberts' decision. Here's part of our exchange:

LEW: For that one percent who have chosen not to buy health insurance, and just to pass the burden on to others, there's this penalty.

STEPHANOPOULOS: But you do concede - and you keep wanting to use the word penalty - you do concede that the law survived only because Justice Roberts found this to be a tax?

LEW: You know, I think, if you look at the decision, which is a very complicated one, there are arguments that support different theories. There was… (crosstalk)

STEPHANOPOULOS: But the argument of Chief Justice Roberts is that it's a tax.

LEW: He - He went through the different powers that Congress has and found that there is a power, whatever you call it, to assess a penalty like this.

STEPAHNOPOULOS: He called it a tax.

LEW: (smiling, no response)

STEPHANOPOLOUS: So you're conceding that?

LEW: I'm saying that it was set up as a penalty for people who choose not to buy insurance, even though they can afford it, and for that one percent, we call it fair.

STEPHANOPOULOS: And he calls it a tax. I'm going to move on now at this point.

Lew's argument is in line with what President Obama told me in a Sept. 2009 interview on "This Week," when he insisted that "to say that 'you've got to take a responsibility to get health insurance' is absolutely not a tax increase."

Watch that exchange here:

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