Fox News host Chris Wallace on Sunday agreed with GOP hopeful Mitt Romney's claim during last week's presidential debate that the Republican nominee had not proposed a $5 trillion tax cut.

"I don’t have a $5 trillion tax cut," Romney had said on Wednesday. "I don’t have a tax cut of a scale that you’re talking about."

"Both sides since the debate have been saying that the other candidate is lying about his position," Wallace told Maryland Gov. Martin O'Malley (D) on Sunday. "The president keeps saying that Mitt Romney is proposing a $5 trillion tax cut. That's not true."

"Wait a minute here," O'Malley replied. "Former Gov. Romney is proposing a 20 percent cut to income taxes, including income taxes for the wealthiest Americans. And I believe a 30 percent cut for corporate income taxes, including for people like big oil that are socking all of us at the pump right now. Any economist can debate whether that adds up to $4.9 trillion or does it add up to $5 trillion? But the fact of the matter is in this debate, we saw Big Bird meet the big lie."

Wallace argued that O'Malley was "mischaracterizing" Romney's plan because the former Massachusetts governor had promised to make the tax cuts revenue neutral by closing loopholes, although he has refused to say which loopholes.

"Gov. Romney has not said what he secret plan is for paying for these $5 trillion tax cuts," O'Malley explained. "Just like he won't talk about what his tax returns have been or how much money he's sheltering offshore."

An analysis by the the non-partisan Tax Policy Center concluded that Romney's plan would reduce revenue by $480 billion in 2015 and $5 trillion over 10 years.

Watch this video from Fox News' Fox News Sunday, broadcast Oct. 7, 2012.