GOVERNMENT appointed animal welfare experts have called for Royal Navy procedure changes after saying they were responsible for detonating four bombs underwater which led to the death of 19 pilot whales, when they became stranded off the north of Scotland four years ago.

Their report released by the Department for Environment, Food and Rural Affairs (DEFRA) said the noise from the explosions was likely to have damaged the whales' hearing, which caused them to drift onto the beach and die.

The SNP called on the Ministry of Defence to give assurances that no more bombs will be exploded underwater in Scottish seas, following the confirmation.

Some 70 long-finned pilot whales swam into the Kyle of Durness, a shallow tidal inlet east of Cape Wrath, Europe's largest live bombing range with 39 left stranded by the tide.

The Royal Navy told DEFRA that munitions disposal had been carried out at Garvie Island for several decades without incident.

The bombs were left over from military exercises in which planes target the small rocky outcrop.

But the report compiled by the Inverness-based wildlife unit of Scotland's Rural College said the Navy's whale-spotting safety practices were "insufficient" and calls for the services to use charges that "burn out" bombs rather than cause explosions.

"Given the potential damage to marine life from the 'high order' explosions of conventional disposal techniques, it is questionable why this method has not been used routinely in the past," it says.

The report explains that four 1,000 pound bombs were detonated at sea by the Royal Navy's Northern Diving Group during the 24 hours before the mass beaching occurred.

Another 250-pound bomb was later detonated after the crisis had begun.

Locals tied to herd the whales back into open water and while 39 became beached, some 20 were re-floated.

However, despite efforts by experts and concerned residents, 19 of the stranded whales died, prompting a government inquiry.

Rob Gibson MSP, who had previously predicted that was the cause,criticised the UK government for taking four years to deliver the report and has written to Defence Secretary Michael Fallon demanding the MOD must give assurances that this will not happen again.

Mr Gibson, the SNP MSP for Caithness, Sutherland and Ross, said: "The fact that it took four years for this report to be published and for the UK government to accept that they are to blame is ridiculous.

"The efforts of the local people in the Kyle of Durness to save the beached whales were incredible - but sadly the animals could not be saved and many died.

"Scotland's seas are blessed with many marine mammals, including more than 20 species of whales, dolphins and porpoises. It is our responsibility, where possible, to do all we can to protect these wonderful and popular species."

He said he wanted Mr Fallon to make a commitment to ensure that the MoD cease exercises in this area and "stop treating the wildlife and residents so appallingly".

The report on the July 22, 2011 catastrophe concluded: "Once the pod was within the Kyle of Durness, navigational error would definitely be a contributing factor to live stranding.

"Munitions disposal operations conducted in the vicinity the day before and during the stranding was the only external event with the potential to cause the stranding.

"The magnitude, frequency and proximity of the multiple detonations in the day prior to the stranding, and the single high order detonation shortly after the beginning of the mass standing were plausible sources of significant disturbance to any neighbouring marine mammals.

"It is probable that the presence of a potentially compromised animal, navigational error in a topographically complex region and the serial detonation of underwater ordnance were the most influential factors in this mass stranding event."

The three initial explosions could have had a "significant detrimental effect on the hearing and therefore navigational competence of any cetaceans in proximity," it adds. The fourth bomb "might have served to drive the animals further inland".

An MoD spokesman said: "The MoD accepts the findings of the Durness Mass Stranding report which identified a number of possible factors that may have influenced events, one of which was the detonation of underwater explosives.

"The recommendations will be considered by the MoD and implemented where appropriate. Additional mitigation has already been put in place during munitions disposal activities conducted since 2011."