The National Transportation Safety Board said yesterday that blame for a 1983 collision between a private plane and an Air Force jet off the North Carolina coast in which a Virginia lawyer and six passengers were killed was shared by both pilots and showed a lack of coordination between civilian and military air controllers.

The NTSB said its members were unable to agree on a single cause for the collision, which occurred as an F4C Phantom fighter intercepted the twin-engine Beech Baron inside restricted air space 20 miles south of Cherry Point, N.C.

Henry H. Tiffany, 47, a flamboyant Waynesboro, Va., lawyer, and his six passengers perished when the wing of the F4C, approaching from the rear in poor visibility, sliced through the small plane's fuselage and cockpit.

The jet, with a two-man crew, returned safely to Seymour Johnson Air Force Base in Goldsboro, N.C.

Tiffany had been imprisoned for two months in 1978 after a plane he was piloting was forced down with engine trouble in Haiti. Officials found more than a ton of marijuana aboard the aircraft and U.S. drug authorities said later that Tiffany was implicated in a major Northern Virginia smuggling ring.

The collision occurred on Jan. 9, 1983, while Tiffany's plane was on the way from the Bahamas to Norfolk. The NTSB report said Tiffany's flight plan called for a required stop in Florida to pass through U.S. customs, but said Tiffany instead was trying to fly directly to Norfolk.

The board faulted Tiffany for failing to adhere to the flight plan and said he also failed to notify controllers when he entered a restricted zone off the North Carolina coast.

Two Phantoms were scrambled after air traffic controllers were unable to identify the plane immediately. The board said the pilot of the Phantom involved in the collision, Capt. John A. Wellers, overtook Tiffany at a higher speed than intended as he searched by radar for the unidentified contact.

The board also faulted Wellers for failing to maintain at least 500 feet vertical separation between the two aircraft, as he had been instructed.

About two minutes before the collision, the report said, Federal Aviation Administration controllers in Washington notified military controllers in North Carolina that they had managed to identify the aircraft as Tiffany's.

Due to a lack of "timely coordination" among military authorities, according to the NTSB, "by the time a termination order was issued to the F4Cs, the collision had occurred." The board also said 5 1/2 minutes passed before military officials notified the FAA of the collision. Under different circumstances, the NTSB said, such a delay "could have been life threatening."