Former Maryland Gov. Martin O'Malley (D) on Monday criticized No Labels for allowing Donald Trump to accept the group's "problem solver promise."

Speaking to the No Labels Problem Solver event in Manchester, New Hampshire, the Democratic presidential candidate said he appreciated taking the "promise" label himself but questioned how Trump could qualify, given his provocative statements.

"Quite honestly, I think that you are watering down and dumbing down your problem solver label when you bestow it on someone like Donald Trump," O'Malley said, drawing applause from the audience.

Get Breaking News Delivered to Your Inbox

"When Donald Trump says things like all Mexicans are rapists and murderers, that's not being a leader. That's not solving problems. There's other adjectives for that -- one of them being racist," O'Malley added. "When Donald Trump says things like we should issue ID cards to all American Muslims, that's not bringing people together. That's not solving problems. That's making a fascist appeal. So I would encourage you not to dumb down this label.

On Monday, the group announced that six presidential candidates had accepted the group's "promise:" O'Malley, Trump, Ben Carson, John Kasich, Rand Paul and Chris Christie.

Accepting the "problem solver promise" would require the candidates, if elected, to work toward creating 25 million new jobs in 10 years, securing Social Security and Medicare for 75 years, balancing the budget by 2030 and making the U.S. energy independent by 2024.

It also requires the candidate to promise to act within the first 30 days in office to work on at least one of the four goals.

No Labels is a non-partisan organization co-chaired by former Sen. Joe Lieberman, I-Connecticut, and former Utah Gov. Jon Huntsman (R). It was created after the 2010 midterm elections to foster bipartisanship.

"Regardless of what one's platform happens to be, in the end, these candidates and somebody who becomes the next president of the United States is going to have to work with Republicans and Democrats and break that impenetrable partisan divide in order to deliver things for the American people," Huntsman said in a video explaining the group's agenda.

No Labels says it doesn't endorse candidates.