Representatives of Prince George's County's 1,300-member public employes union, who have been fighting bitterly with County Executive Lawrence Hogan over a new contract, are taking their grievances to the public.

The campaign complete with bumper stickers and protest posters, is designed to turn sentiment against Hogan, according to Paul Manner, a union official. The 16-month dispute, has left many county workers without cost-of-living pay increases and, a few months ago, resulted in an outside hearing examiner finding Hogan guilty of unfair labor practices.

With a three-month court in injuction barring a strike about to expire, the union's action appears designed to gain public support in the event of a walkout.

This week, the union began printing leaflets and 10,000 bumper stickers -- in Hogan's traditional green and white campaign colors -- which state "Hogan is guilty." Mannner said the union, a local of the American Federation of State, County and Municipal Employees, expects to begin distributing leaflets at shopping malls this weekend and will picket outside Hogan's home and at any night ghaterings he attends.

"If it injures him at all, that's a plus for us," Manners said. "He's never done anything but hurt us and we want to hurt him."

Hogan yesterday dismissed the union effort, which his son and top aide, Lawrence Hogan Jr., said would only help Hogan and add to his name recognition. Hogan also sent legislation to the County Council yesterday that would, if adopted, give the workers represented by the union a 4.7 percent cost-of-living pay increase that all other county employes received last July.

Manner said the union will support such legislation, proivded the cost-of-living figure was amended to 6 percent.

The union's "anti-Hogan" campaign follows months of negotiations, court suits, public posturing and hearings by the county's public employes relations board over the the contract dispute.

While the union and Hogan give different reasons for the stalemate, some of the county's lowest paid workers including prison guards, road crews, housing inspectors and clerical workers still have no contract and the county and the union remain far apart on issues concerning work conditions, employe benefits and privileges for the union leadership.

Although negotiations between the county and the union have been under way since February 1979, the battle intensified -- and emerged into public view -- last February, when Hogan's own negotiators and the union reached a tentative agreement.

That agreement provided for wage increases of 4.7 percent his year and 5 percent next year and was considered by Hogan's aides to be quite favorable to the county.

Although the union membership ratified the tentative agreement, Hogan rejected it because he apparently felt that recent conflicts with political adversaries on the County Coucil over his handling of the labor negotiations would make a settlement of the longstanding dispute appear to be a capitulation.

Hogan has continually maintained that he vetoed the agreement because of several minor economic issues and because it provided too many county-paid benefits to the union's leadership.

As a result of Hogan's rejection of the tentative agreement, the union filed several unfair labor practice charges against the county with the public employes relations board. In March a hearing examiner ruled in favor of the union and stated that Hogan had violated labor laws in rejecting the tentative contract. Hogan has appealed the ruling.