WHAT AN UNPLEASANT and inexplicable surprise Prince George's County Executive Lawrence J. Hogan came up with for his constituents, employees and labor negotiators the other day. Just when everybody at the bargaining table thought that a contract with county workers had been agreed to, Mr. Hogan pulled the adminstration rug out from under his own representatives -- denouncing them for coming in terms with the unions and taking a verbal poke at the county council for what he charged was interference with the negotiations.

As arbitrators scrambled to pick up the pieces, Mr. Hogan was arguing that he rejected the agreement because the county's negotiators had exceeded what he was willing to offer the unions. In a stirring statement of mismanagement, Mr. Hogan said, "I'm displeased with my negotiating team. . . . It exceed the parameters given to them." When a union negotiator asked the county executive how he expected the union to know what he wanted if his own negotiating team didn't know, Mr. Hogan acknowledged that this indeed can be a problem.

Making things all the more confusing were reports from county government officials that Mr. Hogan did too have an advance idea of what the agreement would look like. What got his goat, they said, was a news report saying that the county council had warned the county executive that it would not support him if he committed any unfair labor practices or illegal attempts to enforce a wage settlement. Mr. Hogan's rejection of the agreement, they say, was based not on financial considerations but on his concern that approval might be interpreted as capitulation in the face of the council warning.

Were this merely another in a series of childish political quarrels and practical jokes between a Democratic council and a Republican county executive, taxpayers could dismiss it all with a hoot. But when the consequences of the county executive's undercutting his own negotiators could have produced a totally unnecessary municipal job action, residents have too much at stake to look the other way. Whatever Mr. Hogan may have thought he was accomplishing, it was a reckless way to handle a serious matter.