Gabbard, the vice chair of the Democratic National Committee, told CNN's Wolf Blitzer Monday on "The Situation Room" she was told her vocal support for more debates had made her "no longer welcome to come to the debate."
Gabbard said the message was conveyed to her chief-of-staff from the chief-of-staff of DNC Chairwoman Debbie Wasserman Schultz.
"The prevailing message of that was that because I continued to call for more debates, that I should not go to the debate in Las Vegas," the Hawaii congresswoman said. "The issue here is not about me saying, 'Boo hoo, I'm going to miss the party.' The issue here is one of democracy and freedom of speech."
The New York Times reported
earlier Monday that Gabbard had received a message through her staff about her attendance at the event one day after she appeared on television calling for more Democratic debates. Bernie Sanders campaign then offered her a ticket later on Monday.
"If she needs a ticket, have her give me a call," Jeff Weaver, Sanders' campaign manager, said on CNN's "New Day" on Monday. "I think we have a couple; we can give her one."
Gabbard said she "politely declined" Weaver's offer, not wanting to turn the brouhaha into a "political conversation."
Sanders' campaign has also called for more debates, as has fellow Clinton challenger and former Maryland Gov. Martin O'Malley. Wasserman Schultz, however, has remained steadfast in her decision that there will only be six sanctioned debates for the Democratic presidential candidates.
A DNC spokeswoman told The New York Times that Gabbard was not uninvited, but that the committee communicated that the focus at the debate should be on the candidates present and the difference from Republicans.
"The focus of the debate in Nevada as well as the other debates and forums in the coming weeks should be on the candidates who will take the stage, and their vision to move America forward," DNC press secretary Holly Shulman said in a statement to CNN. "All that was asked of Ms. Gabbard's staff was to prioritize our candidates and this important opportunity they have to introduce themselves to the American people. The Democratic Party is a big tent party and we embrace the diversity of opinions and ideas that come from our members."
A source familiar with the situation said the DNC has tried to reach out to Gabbard, but she has yet to respond.
But another Democratic source familiar with the interaction said Gabbard was in fact uninvited, and that some members of the party are upset with how Wasserman Schultz handled the situation.
Weaver said the Vermont independent senator, running second in the polls to Hillary Clinton, is a supporter of more debates.
"We would love to have debates: The more debates, the better," Weaver said on Monday. "It's healthy for the Democratic Party to have more debates."
Weaver said more debates would keep media attention on Democrats and would feature the left's flank of the party's platform "on the front-burner."