It is understood coastguard crews in Stornoway and Shetland are refusing to carry pumps onboard their helicopters because of safety concerns.

The pumps are designed to help vessels that are taking on water.

But staff are said to be worried that the equipment cannot be properly secured and therefore could be dangerous.

Previous helicopters used by the coastguard – the S61 model operated by Bristows – could have the equipment secured to them relatively easily.

However the coastguard has switched to the S92, which is operated by CHC, and it is claimed that it is no longer as easy to ensure the pumps are properly tied down.

As a result, crews are worried that the heavy equipment could be thrown around if the aircraft got into difficulty.

Lowering the pumps onboard stricken vessels can buy seamen precious time as they battle to prevent their vessels from becoming overwhelmed.

It is not believed that the absence of the pumps will put lives at risk, but saving the vessels may prove less likely without them.

Pumps are carried on military helicopters because they are equipped with suitable tie-down points but coastguard helicopters are often involved in primary responses.

While not currently carrying pumps, the coastguard insist they will continue to fulfil their primary role - the safety of life at sea.

They say the absence of pumps has not in any way eroded their life-saving capability.

New, smaller pumps which will fit on the helicopters have been ordered and should be delivered in the next few weeks.