Relations between Republican Prince George's County Executive Lawrence J. Hogan and the all-Democratic County Council, already strained by repeated conflicts, reached a new low yesterday when the council rejected Hogan's planning commission nominee.

The 7-to-3 vote to reject John Cumberland, a University of Maryland professor, dashed months of behind-the-scene efforts to work out a compromise on the county's appointments to the two bicounty agencies that control many of the zoning and sewer decision that figure in the county's development.

Cumberland's rejection for the Maryland-National Capital Park and Planning Commission signified that the partisan rift in Prince George's is not about to end, particulary when development policies or patronage appointments are at stake.

"There a full-fledged war going on," said one council member after yesterday's vote.

Hogan clearly angered by the vote, responded. "They [council] members are impossible to compromise with. They only want puppets for the developers who control the Democrats."

Most council members said they voted against Cumberland because they felt he wanted to limit development in the county to high-priced homes and businesses.

Yesterday's vote also resulted from Hogan's failure to reach a compromise with the council on several other key appointments on the planning commission and the Washington Suburban Sanitary Commission, which provides sewer and water service to Prince George's and Montgomery counties.

The council and members of the county's all-Democratic delegation to the state legislature wanted to ensure that at least one of the county's three seats on the WSSC remained in Democratic hands.

The Democratic also wanted to persuade Hogan to reappoint one Democrat and appoint a second to the five-member county planning board, which makes up half the bicounty planning commissions. They wanted him to withdraw Cumberland's name because of heavy opposition from developers and the county Chamber of Commerce.

Since last fall, Hogan and various council members and state legislators have tried to reach an agreement on appointments.

"There was offer and counter offer" said one Democrat. "But as soon as we started discussing names it was just no go with Hogan.

According to Hogan the council "kept upping the ante. They wanted the moon and they wanted to keep their flunkies on the board. That's why they rejected Cumberland, an eminently qualified guy.

Council member Gerard T. McDonough, who did much of the negotiating with Hogan, said: "We only wanted some input and ever since he [Hogan] was elected he has given us none. Mr. Hogan has never realized that Prince George's County is not a medieval fiefdom with him as a sort of feudal lord proprietor and the council as the pack of vassals."

Although the council and Hogan have bickered repeatedly over appointments, development policy, personal ethics and other matters since they were all elected 17 months ago, both sides said they believed that compromises could be worked out.

Yesterday that belief was under severe strain, with Hogan threating to ignore the council on all appointments and simply send it one name after another of his own choosing.

"If they don't accept any of them, it'll just give me a good campaign issue," the executive said. "I may never get another appointment approved, but I'm not going to send down puppets."

Responded a council member, "We simply tried to work on cooperation so that we could accomplish some of the things government is here to do. We realize we have something to accomplish and we stand ready and able, but Hogan would have it his way or no way at all."