Dingell said in a letter to NRA President Tom Washington: "I find the conflict between my responsibilities as a member of Congress and my duties as a board member of the National Rifle Assn. irreconcilable."
In a House speech, Dingell said he strongly opposed the crime bill's assault weapon ban as an infringement of gun owners' rights. But he said he was nevertheless supporting the $30-billion bill.
The NRA strongly opposed the bill, and supporters of the measure said it had mounted an eleventh-hour campaign to try to kill it.