With HMS Cumberland tackling Somali pirates off the coast of Africa, the navy is playing an ever-increasing role in protecting merchant shipping.

On Wednesday Foreign Secretary David Miliband said the navy would spearhead a European initiative in the region.

But with two decommissioned destroyers due to be towed from Portsmouth this week alone, fears have been raised that the force is spread too thin.

Admiral Sir Jock Slater said: 'The problem of piracy has been around for centuries but there is no doubt it has recently increased.

'The Horn of Africa is a very problematic area because Somalia is a lawless state, which makes dialogue next to impossible.

'Added to that you have the methods used by the pirates, whereby a few small craft can take a giant ship like the Sirius Star because of the small crew.

'The navy is well-known for its skill in tackling piracy, and the marines clearly had a successful engagement last week. But there is a huge problem with the shrinking size of our fleet.

'Two decades ago the frigate and destroyer fleet was twice what it is, and the simple fact is we can't cover the vast oceans as we would like.'

Fellow former First Sea Lord Admiral Sir Alan West told The News action was long overdue.

He said: 'I first operated in that part of the world back in 1967, and even then there was a problem with piracy.

'The issue is a difficult one that the international community has struggled to come to terms with, but it affects the majority of merchant ships.

'The bulk of the world's fleet is administered from London with the International Maritime Organisation, and so this is very relevant to us.

'It is encouraging that the process has started to alter the legal situation, and reassuring that Royal Navy sailors will be leading the efforts.'