An independent expenditure group in Maryland funded largely by labor unions launched a television ad Wednesday claiming that Attorney General Douglas F. Gansler is “unfit to be governor” because of a pair of controversies that dogged his campaign last fall.

The 30-second spot by “One State, One Future” features television news coverage of stories about Gansler ordering troopers assigned to drive him to speed and run red lights and his appearance at a teen beach party where there was apparent underage drinking.

Those stories broke last fall in The Washington Post and the Baltimore Sun just as Gansler was launching his bid for the Democratic nomination for governor.

Organizers of the group said that the ad is airing on cable stations in Montgomery County, where Gansler lives. And they said it comes in response to Gansler’s “negative campaign,” including two new television ads targeting his leading Democratic rival, Lt. Gov. Anthony G. Brown that debuted Wednesday.

As of May 20, “One State, One Future” reported having more than $460,000 in the bank — enough to allow it be a nuisance to Gansler in the remaining weeks before the June 24 Democratic primary.

The largest donors are labor unions, some with affiliates that have endorsed Brown’s bid for governor. But both Christy Setzer, a spokeswoman for the group, and Justin Schall, Brown’s campaign manager, both said there has been no coordination between the two.

The Gansler campaign said it was unconvinced, however. The group and Brown’s campaign employ the same fundraising consultants and lawyer, which Schall dismissed as evidence of nothing.

“Anthony Brown and his special-interest allies are resorting to dirty personal attacks against Doug and his family to distract from Brown’s failed record of leadership,” Gansler’s running mate, Del. Jolene Ivey (D-Prince George’s), said in a statement Wednesday night.

“If Brown were serious about standing up to special interests and fighting the influence of outside money, he would immediately denounce and halt these personal attacks,” she said.

Donors to “One State, One Future” include political committees representing teachers, building trades unions, firefighters and trial lawyers.

Setzer said the group has no plans to target other races and has as its sole mission to “counter the effect of Mr. Gansler’s year-long negative campaign.”

In November, Brown suggested the three main Democrats running for governor sign a “positive campaign pledge” that include the line that “we will publicly condemn and ask all third-party groups to refrain from any negative advertisement.”

The campaigns never came to terms on such an agreement.

Besides Brown and Gansler, the Democratic primary also includes Del. Heather R. Mizeur (D-Montgomery).