LONDON, August 1, 2008 (AFP) - Rescuers attempting Friday to save a whale stranded on mud flats in southern England appeared to have lost their battle after the animal suffered kidney failure.

The six-tonne (5,440-kilogramme) northern bottlenose whale was re-floated after it became stuck near Hayling Island in Hampshire for around 12 hours when the tide went out.

But blood tests on the animal showed it had suffered irreversible renal failure, probably as a result of dehydration and muscle failure.

Faye Archell, from the British Divers Marine Life Rescue which is leading the rescue, said the whale would probably have to be given a lethal injection as it would be unable to survive even if it could be returned to the open sea.

'At the moment the animal is bobbing around but if and when this animal comes back in... it will have to be euthanised,' she said.

'There's no coming back from renal failure. It's not good news but is what we expect from these cases.'

The northern bottlenose is a deep-water whale which feeds on squid, so experts were unable to explain why it had swum into such shallow waters in Britain.

It was the same species as a whale that became stuck in the River Thames in London in 2006, sparking huge media interest in Britain. That animal died as it was being ferried back out to sea.