Top leaders from both major parties announced formation Wednesday of a bipartisan commission to study ways of updating, and perhaps shortening, the next national political conventions in 1992.

The Commission on National Political Conventions plans to make recommendations to the Democratic and Republican parties well before the next nominating conventions.Frank J. Fahrenkopf Jr., who steps down in January as Republican national chairman, and Charles T. Manatt, former Democratic national chairman, will serve as co-chairmen of the commission. Both said at a news conference that they wanted to update conventions in an era when changing nominating rules and growth of the primary system have taken much of the suspense out of conventions.

Fahrenkopf said the commission would consider "whether or not the convention process cannot be streamlined in some way, to make it crisper, make it cleaner from the standpoint of presenting a program that will attract more Americans to watch it."

He said the panel, which includes some network television representatives, would also "take a hard look at what really the role should be of the media," particularly television, in covering conventions.

He and Manatt said they do not intend to conduct a broader study of the much-criticized primary process.

The commission's establishment is in part a reaction to critics of the convention process who contend the nominating conventions have lost much of their meaning and have been reduced to staged events, no longer meriting the intensive television coverage and media scrutiny that they receive.

Among those serving on the commission are Lee Atwater, manager of President-elect George Bush's campaign and Fahrenkopf's designated successor; outgoing Democratic national Chairman Paul G. Kirk Jr.; and two contenders for the top Democratic party job, Washington lawyer Ron Brown and Michigan Democratic Chairman Richard Wiener.