Swanson says representatives of the American Federation of State, County and Municipal Employees Council 5 approached her earlier this year, seeking her support for unionization.
The DFL attorney general says the same representatives recently threatened threatening to launch a campaign to "demean or disparage" the office if she didn't allow them to proceed.
"If I didn't agree to their demands (union officials threatened) that they would do a blog attack and they would try to plant unfavorable stories in the press," Swanson said. The threats, she said, were made in the past week to Brian Bergson, a top adviser and spokesman to Swanson.
AFSCME's Jennifer Lovaasen disputes Swanson's description of what transpired.
"We never threatened anything. We made a courtesy call to let them know that there were media inquiries. Now the attorney general has also said that AFSCME cannot organize the attorneys in the AG's office. We beg to differ," says Lovaasen.
One point of dispute is whether and how state law would permit assistant attorneys general to unionize.
The tensions came to light as Swanson explained the departures of at least 25 members of her staff since she took office in January. She defended the turnover as natural.
Swanson assumed control of an office led for eight years by her mentor, Democrat Mike Hatch. Hatch ran for governor instead of re-election in 2006. After his loss, he took a position under Swanson.
Swanson said some of the departed employees under her charge - lawyers and legal secretaries among them - left for better-paying jobs. She said there were only "one or two" terminations. Two of the people who left held the title "deputy attorney general."
But at least one former staffer says she was fired after passing out union membership cards. Swanson's office denies the firing had anything to do with union organizing.
Swanson, who had AFSCME's endorsement in last fall's general election, oversees 170 lawyers as part of an overall staff of more than 350 employees.
According to a roster produced by Swanson's office, Hatch saw 75 employees leave the office during his transition in 1999.
She said she met with union leaders earlier in the year about their desire to organize, but she declined to take a position.
"I indicated to the union that I thought that whether a union was formed, or under what terms, was really an issue for the employees," Swanson says. "It's not up to the employer or the management of the office to decide who's going to represent employees or under what terms. And that's what I indicated."
(The Associated Press contributed to this report)