Newt Gingrich called rival Mitt Romney a liar on CBS’ “Early Show” Tuesday morning, declaring both the former Massachusetts governor ’s approach to negative ads and his positions on issues dishonest.

The former House speaker has refused to go negative in ads, even as he attacks his rivals in public for using those tactics. Gingrich has singled out Romney in particular for refusing to disavow negative ads aired by a supportive super PAC.

Asked by correspondent Norah O’Donnell if he thought Romney was a liar, Gingrich said bluntly, “Yes.”

The candidate brushed up against this charge on Sunday, calling Romney “somebody who will lie to you to get to be president, will lie to you when they are president.” On CBS he was explicit.

“Well, you seem shocked by it!” Gingrich exclaimed. “Which part of what I just said to you is false? Why is it that if I’m candid in person and I wanted to be honest in person, that’s shocking ... In the traditional Washington pattern it’s better to be sweet and honest and have this face of saying, ‘Oh, gee, we want to be nice to each other no matter what happens to the American people.’”

Gingrich added that he would support Romney against President Obama, but that he would lose: “Do you really want a Massachusetts moderate who won’t level with you to run against Barack Obama who, frankly, will just tear him apart? He will not survive against the Obama machine.”

Romney responded mildly on conservative radio host Laura Ingraham’s show. “Well I don’t know why he is so angry," Romney said. “I think he is a good guy.”

In recent days Gingrich has acknowledged that his anti-negative strategy is failing and suggested that he would start attacking Romney’s record in New Hampshire. Today’s charge is a sure sign of a nasty fight brewing between these two.