A Prince George's County Circuit Court judge yesterday overturned a ban on abortions in county hospitals and ruled that County Executive Lawrence J. Hogan exceeded his authority last August when he issued the order prohibiting such operations.

Judge Howard S. Chasanow ruled that Hogan's position as county executive allows him to enforce laws but does not give hime the right to create a new law, which the judge said the abortion ban amounts to. Enacting legislation is the prerogative of the county's legislative body, the County Council, the ruling said.

As the result of Chasanow's ruling, which took effect yesterday afternoon, any woman now may legally obtain an abortion at either Greater Laurel-Beltsville Hospital or Prince George's General Hospital and Medical Center, one of the largest hospitals in the state. Attorneys for the county, however, said they do not expect doctors to perform abortions at the hospitals until Chasanow has ruled on a county request that enforcement of his order be delayed.

Starting Aug. 11, when Hogan issued his order, the two county-owned hospitals were prevented from performing such procedures except in life-threatening cases. The order was challenged several weeks after it went into effect by two pregnant women who were denied abortions at the hospitals and by the medical staff of Prince George's General.

After hearing the two challenges, Chasanow ruled that "the crucial issue is whether the county executive exercised his executive authority or whether he was in fact exercising legislative authority which is exclusively delegated to the county council. We hold that in adopting [the ban,] the county executive exercised the policy and law-making power specifically delegated to the county council and therefore [the ban] must be declared null and void."

The judge also indicated in his ruling that Hogan's order was invalid because the Maryland legislature had passed laws permitting such operations. Chasanow's ruling did not address the constitutional question of whether a county government in fact may prohibit women from obtaining abortions.

Prince George's County Attorney Robert Ostrom said yesterday that the county will ask Chasanow to stay his order and let the abortion ban continue in effect until a full appeal of the cases can be heard by the Maryland Court of Special Appeals. Ostrom said he expected Chasanow to make a decision on a stay by the end of the week.

However, Stephen Friedman, an attorney who represented both women who challenged the abortion ban, said, "as of 1:30 p.m. today [when the order was signed], the county is permanently prevented from enforcing the ban. If anyone goes in and is prevented from getting an abortion, I personally will go in and ask that the county executive be held in contempt of court."

Lawrence J. Hogan Jr., son and top aide of the county executive said that he was "disappointed with the judge's decision," but that the executive's staff is preparing legislation that would permit the county to prohibit abortions. He said the staff will forward the proposed legislation to the County Council for its consideration.

"Although we disagree with the judge's decision and will appeal it, in the meantime we will ask the council to enact legislation to do the same thing" as the overturned execuitve order, he said. About 100 elective abortions were performed each year at the two county hospitals before Hogan issued his ban.

County Council administrator Samuel E. Wynkoop Jr. said that before the council considers any legislation on the abortion issue, it will ask the county attorney and the state attorney general whether state laws permitting abortions in most instances would prevent the council from enacting a ban.

Any consideration of an abortion ban by the County Council is likely to continue the intense debate that has engulfed the county since Hogan issued his order last summer. Since that time, county officials and local newspapers have received hundreds of telephone calls and letters both praising and condemning Hogan for his actions, and the attorneys and the doctors who challenged the abortion ban also have been deluged with supportive and threatening letters.