Vets took the decision to put down the creature, which had been discovered on the shoreline at Cramond in the early hours of the morning.

Marine rescue volunteers and fire crews had helped to move the white-nosed dolphin to a stretch of the Firth of Forth, where it was refloated and could have been helped back to the open sea.

But shortly after 1400 BST the decision was taken to end its life.

I'm afraid it's a rather sad outcome

Gidona Goodman Edinburgh Veterinary School

Gidona Goodman, from Edinburgh Veterinary School, said blood tests had prompted the decision.

She said: "I'm afraid it's a rather sad outcome.

"After looking at the body condition, there seems to be a bit of weight loss and quite a few teeth are missing, indicating this is an older animal and it really wouldn't be fair to refloat it.

Blood tests

"It probably has not such a good body condition, it might also have an underlying disease as well. So a decision has been taken to euthanase the animal."

She later confirmed that blood tests had shown signs of infection and dehydration.

The dolphin was expected to be taken to an animal laboratory for a post-mortem examination to be carried out in an attempt to establish why it became stranded.

The decision came after the dolphin had been lifted onto a sheet and moved about 200 metres into the water.

Drugs tube

The operation took about 40 minutes and involved stopping the procedure every 10 yards to roll the mammal onto its stomach and bathe it in the water.

During the rescue attempt, it was given food via a tube and antibiotics were administered.

The dolphin had been discovered trapped on the beach by two passers-by at about 0430BST on Friday.

Police and emergency services were alerted and the rescue and refloating operation began shortly after 0700BST.