RICHMOND, Va. (AP) _ Oliver North, whose felony convictions were overturned by a federal appeals panel, criticized Sen. Charles S. Robb for backing federal appeals judges North said are too soft on criminals.

North attacked Democrat Robb's votes this year to confirm Rosemary Barkett for the 11th U.S. Circuit Court of Appeals and H. Lee Sarokin for the 3rd circuit.

''Chuck Robb talks tough about crime, but he's really soft on crime,'' the Republican challenger said at a news conference Wednesday.

Robb called North's comments ''incredible.''

''If it hadn't been for a couple of soft-on-crime federal judges, he'd be in the slammer and certainly wouldn't be able to run for federal office,'' Robb said.

Both judges were endorsed by their senators and police organizations in their states and received the highest rating of the American Bar Association, Robb said.

North said his Iran-Contra convictions, thrown out in 1990 by the U.S. Circuit Court of Appeals in Washington, D.C., differed from cases in which Barkett and Sarokin supported appeals by convicted murderers.

Later Wednesday, North's supporters turned out in force when he showed up in Robb's stronghold, suburban northern Virginia. The two candidates campaigned a few hundred yards from each other at a Halloween parade in Vienna. Chanting ''Ollie 3/8'' and holding enormous banners and signs, North supporters outnumbered Robb marchers.

Robb joked that he should have appeared in costume. ''I suppose if I really wanted to scare the daylights out of everybody, I would dress as my opponent,'' he said.

Earlier, Robb and independent candidate Marshall Coleman called North reckless for saying Social Security should be made voluntary for ''the next generation'' of workers. North retreated, saying he would not support making Social Security optional if it would leave the program insolvent.

Also Wednesday, the Rainbow Coalition, a political group founded by Jesse Jackson, released research showing that North received contributions totaling more than $38,000 from 41 people or families who gave to former Klan leader David Duke's political campaigns.

North's deputy campaign manager, Mark Merritt, criticized the report as an attempt to inject race into the campaign, and said, ''We're not going to take the bait.'' North has said he is offended by any comparison to Duke, who ran unsuccessfully for governor of Louisiana and the U.S. Senate.