The presidential campaign of Sen. Bernie Sanders filed a lawsuit Friday against the Democratic National Committee, arguing that the party had unfairly suspended the campaign's access to key voter information.

The suit came hours after campaign manager Jeff Weaver acknowledged at a Washington news conference that Sanders staffers had improperly reviewed information gathered by rival Hillary Clinton earlier in the week.

But he accused the DNC of overreacting to the breach by suspending the Sanders campaign's ability to access the computer system containing information about Democratic-leaning voters, including data the campaign had gathered about its own supporters.

The messy public brawl threatened to overshadow Saturday's third Democratic presidential debate and cast doubt on the DNC's ability to manage the sophisticated data tools necessary for the party to win the White House next year. And it sparked significant suspicions among Sanders supporters that the party was conspiring to give a boost to Clinton.

DNC Chairwoman Debbie Wasserman Schultz rejected that allegation late Friday, alleging that Sanders staffers had exploited a software error to essentially "steal" data from Clinton's campaign. Wasserman Schultz said the party would not allow Sanders access to the critical database again until his campaign agreed to an independent audit of what happened.

The suit, filed in federal court in Washington, argued that under a contract between the DNC and the campaign governing the data system's use, formal notice in writing is required if either side believes the other has violated the deal. In addition, each side is supposed to be allowed 10 days to address any concerns, the suit said.

"The DNC may not suspend the Campaign's access to critical Voter Data out of haste or desperation to clean up after the DNC's own mistakes," the suit says.

The voter data are heavily used to raise money, and the Sanders campaign estimated that it is losing $600,000 a day in "critical fund-raising and publicity opportunities" without access to the files.

The incident strained the relationship between the campaign of an upstart Vermont senator who until this year has run as an independent and a national party his supporters have long accused of favoring Clinton.

Weaver accused the party of purposely sabotaging Sanders by refusing to restore access to the voter information. "By their action, the leadership of the Democratic National Committee is now actively attempting to undermine our campaign," Weaver said. "I think if you look at the pattern of conduct . . . it looks like in this case they're trying to help the Clinton campaign."

NGP-VAN, the computer vendor that provides Democrats with detailed information about voters, has said that a computer error on Wednesday briefly allowed the campaigns to review information that had been gathered by their rivals.

The company maintains a master voter list for the DNC and rents it to campaigns, which then add their own, proprietary information gathered by field workers and volunteers. Firewalls are supposed to prevent campaigns from viewing data gathered by rival campaigns.

The Sanders campaign has acknowledged that several of its staffers probed the system during the time of the error cited by NGP-VAN. One operative, data director Josh Uretsky, was fired as a result of the incident. Weaver said the actions of several others are being reviewed.

Landing at the airport in Manchester, N.H., ahead of Saturday's debate, Wasserman Schultz said that Sanders himself was unaware of the breach until she called to discuss it 24 hours after it took place. "He was stunned," she said. "I know that Sen. Sanders had absolutely nothing to do with this. . . . Unfortunately, he has staff who acted inappropriately, and they need to be held accountable."

The severity of the data breach itself remained an issue of serious dispute Friday.

Audit data from NGP-VAN and provided to the Washington Post by the Clinton campaign showed that four Sanders staffers conducted 24 separate searches of Clinton data during a 40-minute window Wednesday, targeting early voting states and searching for lists of voters most and least likely to support Clinton.

The logs show that in some cases, the staffers saved the search results in new folders within the system.

"This was a very egregious breach and our data was stolen. This was not an inadvertent glimpse into our data," said Clinton's campaign manager, Robby Mook.

On CNN, Clinton campaign spokesman Brian Fallon accused the Sanders staffers of acting "like kids in the candy store."

"They went hog wild, downloading as much data as they could," he said.

Uretsky, however, told the Post that he and the others conducted the searches of Clinton data after they discovered the software glitch only in an effort to discover the extent of their own data exposure. "We intentionally did it in a way that was trackable and traceable so that when they did an audit they would be able to see exactly what we did," he said.

Uretsky said there was no attempt to take Clinton information out of the software system.

Weaver blamed the software vendor for the breach, which allowed all campaigns to access one another's data for a time. He said that the Sanders campaign had quietly alerted the DNC to problems with the system in October.