Virginia Gov. Charles S. Robb's administration today unveiled a package of anticrime bills that would allow police to make more arrests without warrants and bring longer sentences for crimes committed with guns, harsher fines for drug dealers and changes in the sentencing of the criminally insane.

Aides to Robb and Attorney General Gerald L. Baliles called the package a "responsible start" toward deterring crime and predicted that most of its measures would win approval in the legislature.

It seems likely, however, that portions of the package will run into tough opposition in the House of Delegates, where key lawmakers have long held that mandatory sentences are unsuccessful in deterring crime and only crowd prisons. Police also voiced skepticism about the effectiveness of the package, while civil liberties advocates complained that some of the proposals could jeopardize the individual rights of Virginians.

"I think this program is largely symbolic," said Lawrence Sherman, director of research at the nonprofit Police Foundation.

Included among the proposals were measures that would:

Increase the penalty for use of a firearm in the commission of a felony from the present mandatory one year in prison to three years imprisonment on the first offense. Second offenders would receive a mandatory five-year sentence, up from the current three years.

Establish a verdict of "guilty but mentally ill" to be used in criminal cases. Under such a verdict, a criminal defendant would first be granted psychiatric treatment and then serve the remainder of his sentence in prison. Current law provides that a defendant who is found to be insane at the time of the crime may be released from custody after psychiatric treatment.

Allow police to make arrests without warrants in misdemeanor cases involving assault and battery and destruction of property. Under present law, police may make warrantless arrests only when they have good reason to believe that a suspect has committed a felony.

Raise to $200,000 the maximum fine that can be imposed on a defendant found guilty of manufacturing or distributing certain drugs, including heroin and cocaine. The present maximum fine is $25,000.

Change the state's exclusionary rule to allow courtroom use of evidence gained from what are presently considered illegal searches, if it can be proven that police made a good faith effort to conduct the search properly.

Expand the current wiretap statute, allowing wiretaps to be conducted in kidnaping, robbery, murder and felony marijuana cases.

Neither Robb nor Baliles, who were on a good-will tour of Roanoke with legislators today, made any public statement in support of the package of bills, many of which have been introduced by various legislators in the past.

George Stoddart, Robb's press secretary, rejected suggestions that the governor was trying to distance himself from the bills. "I think you'll find as you deal with the governor more and more . . . that he sort of downplays things," Stoddart said.

Legislators said that the package's opponents will include the powerful coalition of defense attorneys who run the House Courts of Justice Committee, the panel through which most of the bills must pass. Del. C. Hardaway Marks (D-Hopewell), a defense attorney and the committee's chairman, today expressed reservations about the firearms sentencing measure, which opponents said would swell the state's prison population by 1,500 inmates by 1990.

"Philosophically, I am really opposed to any type of mandatory sentences," Marks said. "There might be circumstances where a judge could better rehabilitate and punish the felon."

Opponents conceded, however, that the governor's package will benefit from the political fears of the 100 House of Delegates members who face reelection battles this fall. "Everybody's read the polls that tell them people are worried about crime," one legislative opponent said. "I think for that reason many of these bills will enjoy a lot of support."

Chan Kendrick, director of the Virginia chapter of the American Civil Liberties Union, was critical of the proposed change in the exclusionary rule. He argued that it would encourage police to conduct illegal searches and seizures. "You begin to corrupt the system when you allow police to break the law in order to enforce it," he said.

But administration aides insisted the measure was merely an effort to allow police to do their jobs. "Neither the governor nor the attorney general nor any member of the administration is proposing anything that is a gross violation of anyone's civil liberties," said David Hathcock, the attorney general's spokesman.