The two men had to be cut free by a fire crew before a helicopter crew airlifted them to Wansbeck District Hospital, one suffering from a broken shoulder and the other a cracked rib.
A colleague, who seconds before had been in the truck with them, last night described the "awful" moment the truck slipped over the edge.
He said he had heard a "tremendous bang" and feared for the worst as the truck lay on the beach below.
The two coastguards in the truck had been involved in a rescue operation, after three men and a boy had got into difficulty half a mile out to sea, when their cabin cruiser, called Double Trouble, began to take in water.
The cruiser was brought safely back to shore, with the help of a fishing boat called Bona Venture, whose crew had alerted the coastguard, and a lifeboat from Newbiggin.
Mike Bradley, coastguard station master at Newbiggin, who had got out of the Nissan Navara truck seconds before it slid over the cliff edge, told of the drama last night.
He said: "It slipped off a muddy track as they moved off parallel to the coast. I was only four metres away, but I had my back turned to them when it began sliding. The first I heard about it was a tremendous bang.
"They were a good metre in from the edge, but the conditions were horrendous. I thought the worst at the time and both my colleagues were pretty ill."
Humber Coastguard received a call at 8.30am from Bona Venture saying they had seen a hand-held red flare coming from a small cabin cruiser.
The cliff fall happened at around 8.50am as the two coastguards were driving off to get a good vantage point, from which to help guide the boat back to shore. It is thought the vehicle rolled over twice before landing on its roof.
Coastguard Area Operations Manager Keith Vardy said there would be a full investigation into the cause of the accident.
He said: "I would like to send my sincere best wishes to the two coastguard rescue officers and wish them a speedy recovery from any injuries they may have incurred."
A Northumbria Police spokeswoman said they had been alerted about the cabin cruiser's plight at around 8.30am.
She said: "A land and sea rescue operation was launched involving Her Majesty's Coastguard and the RNLI. In the meantime two coastguard rescue officers were travelling to the scene by land.
"As they approached Beacon Point their vehicle rolled over the cliffs and landed on the sand below on its roof. Both occupants were cut free and taken to Wansbeck District General Hospital."
Timetable of events
8.30am: Coastguards receive a call from the fishing vessel Bona Venture to say the cabin cruiser Double Trouble is in danger of sinking half a mile out to sea from Beacon Point.
8.42am: Newbiggin-by-the-Sea lifeboat arrives at the scene and begins towing Double Trouble back to shore. They arrive back in Newbiggin at 9.05am. The crew of Double Trouble sort out the boat's fault, and return to sea, arriving back in Amble at 12.31pm.
8.51am: Two coastguards taking part in the rescue operation plunge over a 20ft cliff at Beacon Point.
8.52am: RAF Boulmer, Northumbria Fire and Rescue Service, the North-East Ambulance Service and Northumbria Police are alerted.
9.09am: The two coastguards are flown to Wansbeck District Hospital by RAF Boulmer.
12.40am: The first coastguard is released from hospital suffering from a broken shoulder.
5pm: The second coastguard is released from hospital suffering from a cracked rib.
Written by The Journal - Newcastle-upon-Tyne
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