The American Bar Association's policy-making House of Delegates today recommended sweeping changes in the grand jury system - including allowing defense lawyers in the jury room - that the Justice Department strongly opposed.

The proposals are aimed at ending what an ABA committee called "abusive" elements of the 800-year-old grand jury sytem, which developed under English common law to protect citizens from the king but which has now become a tool of the nation's prosecutors.

While the ABA's action has no force of law, it has influence with Congress and state legislatures, which can pass measures revising the system.

An aide of Rep. Joshua Eilberg (D-Pa.) who has introduced a bill in Congress to revise the federal grand jury sustem along the lines recommended today by the ABA, said the measure would have no chance of passing without the support of the organized bar.

Attorney General Griffin B. Bell, who led a Justice Department team opposing parts of the recommendations before the ABA delegates, promised that the next battle would be in testimony to Senate and House committees considering changes in the federal grand jury system.

Beil especially opposed the provision that would allow witnesses to have their lawyers in the grand jury room. He called it "a lawyer's relief act" that would "generate plenty of business for lawyers."

Most grand juries, including those in federal courts, now allow witnesses to consult with their attorneys in an anteroom after every question.

Allowing a lawyer in the grand jury room with his client would fundamentally change the system, and federal prosecutors who lobbied ABA House of delegate members here all week said it would hamper their investigations of white-collar organized crime.

"Putting a lawyer in the grand jury room will invariably lead to impeding the investigation," Benjamin R. Civiletti, head of the Justice Department's Criminal Division told the delegates.

Richard E. Gerstein, however, who has had experience on both sides of the grand jury in his 21 years as chief prosecutor in Dade County (Miami), Florida, replied, "It's the only stage of the criminal proceeding where a person does not have a right to counsel."

Gerstein, who headed the ABA efforts for grand jury revision against state and federal prosecutors, gets much of his political support from an association of grand jury members. But he was also the subject of a corruption investigation by a special grand jury called by former Florida Gov. Claude Kir, was clearre.

Gerstein said the grand jury needs to be changed if it is to remain a vital part of the criminal justice system. Hesaid it was especially misused during the Nixon administration when grand juries were set up in cities far from the scene of a crime and used to harass antiwar dissidents. He noted that a Seattle grand jury, for example, investigated the bombing of the Capitol in Washington, D.C.

The ABA also took another action opposed by the Justice Department: The legal organization recommended that prosecutors be barred from involking a device called "use immunity." That device allows witnesses to be given immunity from prosecution for answers they give to a grand jury, but they still can be prosecuted on the basis of other evidence.

The ABA recommended that prosecutors instead be allowed to grant only a broad immunity, called "transactional immunity," under which a witness could not be prosecuted under any circustances for the crime being investigated. Under the ABA proposal, prosectors would be required to prove to a judge that such broad immunity is necessary before it could be granted.