JACKSON HOLE, Wyo. - In a new television ad released today, Mitt Romney accuses President Obama of lying and asks how voters can trust him to lead if he "doesn't tell the truth."

The ad, titled "No Evidence," is the campaigns clearest and most aggressive push back thus far against claims by the president's campaign that Romney outsourced jobs while working at the private equity firm he founded, Bain Capital. The claims have been largely debunked by fact-checking organizations.

Watch the ad here:

"When a president doesn't tell the truth," the ad opens, "how can we trust him to lead?"

The 30-second ad, which appears on Romney's website adjacent to a form on which voters can sign up to "receive the truth" via e-mail from the campaign, uses text from the Washington Post that labels Obama's outsourcing attacks "Misleading, Unfair and Untrue."

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"There was no 'evidence' that Mitt Romney shipped jobs overseas," a narrator says.

The ad also uses then-candidate Hillary Clinton's famous "Shame on you" line she delivered during the 2008 raise in reference to Obama's attacks on her.

"Candidate Obama lied about Hillary Clinton," the ad's narrator says.

"But America expects more from a president," it says. "Obama's dishonest campaign, another reason American has lost confidence in Barack Obama."

Romney himself swatted back at the attacks earlier this week during an appearance in Colorado, when he referred to Obama as the "outsourcer-in-chief," reminding voters there that if they're worried about outsourcing, they should be concerned about the president and not him.

The Obama camp won't directly respond to Romney's new ad, instead pointing to a Boston Globe report suggesting that Romney is the one being less than truthful.