The Prince George's County Council yesterday tentatively cut 30 positions from the police department budget despite a 12 percent increase in the number of police calls in the county last year.

If the council gives final approval, the authorized strength of the county police force will drop to 864 persons. The department had 85 more positions three years ago.

In the last year, overall crime in Prince George's rose 4 percent, with a 6 percent increase in the number of murders.

Police Chief John W. Rhoads, meeting with the council during its budget work session, was not happy with the proposed reductions. "We will be extremely hard pressed to carry out our function with the manpower cuts we are facing," he told council members.

If the manpower reduction is ordered, the positions will be eliminated through attrition, officials said.

The five-hour work session ended with the tentative decision to cut $719,000 from the $29.6 million police budget proposed by County Executive Lawrence J. Hogan. The council is considering another proposal to slash $310,000 that would cover the cost of gasoline officers use in driving their squad cars home after work.

One of the most controversial cuts was $417,710 that Hogan wanted to use to hire a black officer from outside the department to fill the vacant post of lieutenant colonel. Hogan has pledged to increase the number of black officers in management positions.

Councilman Parris N. Glendening, who led the fight against the appropriation, argued that Hogan's plans should be executed by charter amendment.

"I don't see anything wrong with an idea that's going to bring minorities onto the force," replied Loyd E. Wilson, Jr., a black councilman, who voted against the motion to delete the $41,710 request.

The item that caused the lengthiest and most heated debate of the day was one the council had no control over-educational incentive pay for police.

"I just want to make it clear right now that I will not approve another police contract which continues this program," Council Chairman William B. Amonett said. "We simply cannot afford it."

Under the program, some officers receive as much as 20 percent of their pay depending on how much college education they have. The program was instituted seven years ago in order to, in the words of Glendening "try and eliminate the term 'police mentality.'"

The educational incentive pay is part of the current police collective bargaining contract, so the council could not touch it. But frustated members did pass, by a 7-to-3 vote, a resolution proposing that it be eliminated from all future contracts.

The council added to the budget in only one area, putting back $27,500 left out by Hogan for the job of public information officer. Hogan, following the recommendation of a report by his friend and campaign press secretary Lewis Helm, asked that spokesman John Hoxie's job be eliminated.

But the council, after several members expressed strong support for Hoxie and the position, voted unanimously to put the money back in the budget.

"I am in favor of centralized government," said council member Sue V Mills. "But I don't favor centralizing public information. It could lead to both manipulation and suppression of information and the public should have." CAPTION: Picture, JOHN W. RHOADS . . . not pleased by proposal