Bernie Sanders Bernie SandersOutrage erupts over Breonna Taylor grand jury ruling Dimon: Wealth tax 'almost impossible to do' Grand jury charges no officers in Breonna Taylor death MORE's campaign says it notified the Democratic National Committee months ago of glitches in the party’s voter file that made sensitive information available to rivals, well before Sanders fired a staffer who accessed information from front-runner Hillary Clinton Hillary Diane Rodham ClintonDemocratic groups using Bloomberg money to launch M in Spanish language ads in Florida The Hill's Campaign Report: Presidential polls tighten weeks out from Election Day More than 50 Latino faith leaders endorse Biden MORE’s campaign, according to a report by ABC News.

Michael Briggs, a Sanders campaign spokesman, told ABC News that the “vendor who runs the DNC's voter file program continues to make serious errors” and that the “the firewall between the data of different Democratic campaigns” has failed “on more than one occasion.”

“Our campaign months ago alerted the DNC to the fact that campaign data was being made available to other campaigns. At that time our campaign did not run to the media, relying instead on assurances from the vendor," Sanders campaign spokesman Michael Briggs told ABC News.

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But the DNC this week suspended the Sanders campaign’s access to the data after learning that a campaign staffer accessed Clinton campaign information.

Briggs said the firewall went down again on Wednesday and that it fired the staffer after he “accessed some modeling data from another campaign.”

“That behavior is unacceptable and that staffer was immediately fired,” Briggs said to the network in a statement.

All three Democratic candidates have access to the DNC’s voter file. It acts as a two-way street, allowing candidates to rely on the party’s data to help target voters while also sharing campaign specific data with the party. While the party is able to see the master file, candidates are not supposed to be able to access data obtained by their rivals.

DNC Chairwoman Debbie Wasserman Schultz in an email obtained by The Hill on Friday adds more details on the situation and the party’s reaction. It says that the Sanders campaign had access to “voter targeting data” from Clinton’s campaign for about 45 minutes, emphasizing that no financial, donor or volunteer data was exposed.

The letter adds that the error did not lead to any public exposure of the data, only between the campaigns, and that the DNC’s vendor is investigating what went wrong and if anyone else had improperly accessed the data.

It also lays out the stipulations for Sanders to regain access to the voter file: “until the DNC is provided with a full accounting of whether or not this information was used and the way in which it was disposed.”

Josh Uretsky, the fired Sanders staffer, told ABC News in an interview that his actions were not nefarious and that he had tried to investigate the failure while being sure to leave a record of his actions to prove his honest motives.

“The breach was in no way our fault. I saw it and attempted to investigate and attempted to do it in a transparent manner,” he told the network, adding that he does not believe the campaign took any data or tried to “gain anything out of it.

“We saw a security breach and we tried to assess it and understand it…I knew full well that I was creating a record that the administrators could see.”

While the Sanders campaign is downplaying the revelation, a person familiar with the breach told The Associated Press that campaign staffers saved information and searched Clinton’s information 25 times.

Democracy for America, the major progressive group that endorsed Sanders on Thursday, panned the DNC’s decision in a statement.

"The Democratic National Committee's decision to attack the campaign that figured out the problem, rather than go after the vendor that made the mistake, is profoundly damaging to the party's Democratic process,” Charles Chamberlain, the executive director for Democracy for America, said.

“DNC leaders should immediately reverse this disturbing decision before the committee does even more to bring its neutrality in the race for President into question."