A £15M fighter jet crashed into the North Sea when a tiny metal pin became dislodged.

The Tornado spun out of control after a mechanical accident, an investigation has discovered.

The pilot and navigator ejected before impact when the Tornado GR4 stopped responding and plummeted into the water off the Northumberland coast in July 2004.

An 18-month investigation by the Ministry of Defence revealed that vital gears regulating the flaps were useless after the locking pin dislodged and became jammed in the mechanism.

The aircraft began to roll sharply and, after becoming locked in a flat spin, the pilot gave the order to eject at 10,000ft.

A spokesman said: "The inquiry concluded that the cause of the accident was the loss of control of the aircraft and the subsequent irrecoverable spin."

Two Sea King helicopters from RAF Boulmer, in Northumberland, and RAF Gannett, near Prestwick, Scotland, were scrambled to find the men.

They were rescued within 25 minutes of the accident from their own dinghies. Neither was injured, but the aircraft was a write-off.

The plane had been on a training exercise from its base in RAF Marham, in Norfolk.

Defence chiefs have called for several improvements to be made as a result.