WASHINGTON (AP) _ Sen. Albert Gore Jr.'s presidential campaign is asking the Federal Election Commission to rule on the legitimacy of a reporting practice two Democratic presidential rivals used.

The Gore campaign filed its request for a ruling Wednesday asking the FEC for an advisory opinion on the practice, which was used by Democrats Richard Gephardt and Michael Dukakis to avoid counting against spending limits half the cost of their television commercials broadcast in Iowa.

Gore campaign spokesman Arlie Schardt said today that Gephardt was ''obviously busting the cap by a mile in Iowa,'' where he finished first in the Democratic caucuses on Monday.

Gephardt counted half of the ad costs against the federal limits on spending in one state and counted the other half as fund-raising expenses, not counted against the state limit. Gephardt officials contended that the ad constituted a solicitation for money as well as votes.

Schardt said the Gore campaign did not intend to engage in the same reporting practice in the South, where Gore has pinned his hopes, or elsewhere.

''We absolutely are not trying to do the same thing in the South,'' he said. ''We just don't think other people should be able to violate the spending limits that other people are abiding by.''

Gore's campaign did not specifically cite the other campaigns in its filing but asked whether the approach would be legal. It asked for an advisory opinion within 20 days.

Federal campaign spending laws require candidates who accept federal matching money to abide by spending ceilings calculated for individual states' caucuses or primaries.