Democratic lawyers who have been representing the Virginia Department of Highways in condemnation cases for 20 years and longer are rapidly being replaced by Republicans hired by J. Marshall Coleman, the first Republican attorney general in the state's history.

Coleman's patronage appointments of the lawyers, who are hired on an hourly basis and paid a total of about $800,000 a year in fees for highway work, has touched off strong protests by senior highway department officicals.

Retiring Highway Commissioner John E. Harwood said in an interview he fears the changes could result in higher land acquisition costs for tax-payers because of delays and higher court awards to landowners.

"I'm very upset about it," Harwood said. He added that he fears some of the new Republican lawyers will be inexperienced in condennation cases and will be pitted against "very competent attorneys for landowners."

Coleman was vacationing at a state-owned cottage on the Camp Pendleton military reservation in Virginia Beach yesterday, but his office issued a written statement saying that his patronage appointments are consistent with practices of past Democratic attorneys general.

He also said he expects the changes he makes "to improve services in areas where it has been lax."

Anson Franklin, who was Coleman's campaign manager last year and is now his administrative aide, said in an interview, "We have had reports that lawyers working for the state in some areas, especially rural areas, have not worked as hard as they should in preparing their cases and that judgements for landowners have been higher than they should be.

"To say that we are taking a finely tuned and well-honed condemnation machine and junking it is ridiculous."

Coleman said in his statement that the appointment of attorneys always has been openly political. "As a practical matter, most fee attorneys named by a Republican attorney general will be Republican and those appointed by a Democrat will be Democrats," he said.

"The change may seem dramatic because there has never been a Republican attorney general up to now. Most if not all of the highway attorneys named by my predecessors were in fact Democrats.

Coleman added: "The attorney general should be able to appoint persons he knows and respects. Most of my associates around the commonwealth are Republicans."

Former Attorney General Andrew P. Miller, now the Democratic party's nominee for the U.S. Senate, made major changes in the patronage system in 1970 by ending the assignment of condemnation cases to state legislators, assigning full-time staff lawyers to handle routine cases and reducing the number of firms engaged for condemnation trials from more than 100 to 50.