By Alastair Lawson BBC correspondent in Chittagong

South Asia's ship-breaking yards are expecting more business following the recent sinking of the single hulled tanker, the Prestige, off the Spanish coast.

We know that it's a dirty business, but its work that has to be done

Mohamed Mohsin, managing director, shipbreaking company

The outcry which followed the huge oil spill prompted organisations such as the United Nations and European Union to call for a ban on single hulled tankers to be imposed as soon as possible.

They argue that the vessels are not strong enough to carry large amounts of toxic cargo in environmentally sensitive areas.

That means that before too long there will be no option for these ageing vessels other than to turn them into scrap metal.

Over 90% of the world's annual crop of around 700 condemned ships now end their lives on the beaches of India, Pakistan and Bangladesh.

Thousands of labourers are employed to take the vessels apart by hand for scrap metal.

But many of them are working in dangerous conditions and environmental groups claim that the whole process causes too much pollution.

Dirty work

In the ship-breakers yard on Potenga beach in the southern Bangladesh port of Chittagong, nearly 20 vessels stand side-by-side in various stages of dissection, yawning to expose their cavernous holds, spilling pollution onto the tidal flats.

Technology is often rudimentary

The workers are exposed to numerous risks: falls, fires, explosions and contact with various kinds of toxic chemicals.

"We know that its a dirty business," explains Mohamed Mohsin, managing director of one of Chittagong's largest ship-breaking companies, "but its work that has to be done, and no-one else in the world seems able to do it as competitively as us.

"All too often the ships which my workers break contain toxic substances which harm my men," he told the BBC.

"But if the ships aren't broken we don't get paid, so we have to do it."

Around 1500 workers in Mr Mohsin's Chittagong yard earn roughly $2 a day to tear apart the steel carcasses of condemned vessels.

Most workers do not wear protective clothing.

Many do not even possess gloves to stop their hands being cut by the huge lengths of sheet metal which are sent to scrap yards.

Like other ship-breaking yards in South Asia, what little technology that exists is often rudimentary and unsafe.

There are reports of cable winches snapping and unexpected explosions.

Everything in the Chittagong yards is done by hard labour and sweat.

Low profits

The Bangladesh ship-breakers may be one of the lowest paid labour forces in the world, but the men say that they are willing to brave the dangerous conditions.

"It's tough here," says 15-year-old Abdul Fazim. "We are not allowed to join a union and the hours are long.

"But it provides us with an income when otherwise we would all probably be without work."

Cost-efficiency means more business

Most shipyards operate on a narrow profit margin.

Every part of the ship is recycled right down to the ship's brass bell and other memorabilia is for sale.

The ship's steel plating is made into low grade iron reinforcing rods which are used by Bangladesh's building trade.

But despite international concerns about conditions in South Asia's shipyards, owners like Mohamed Moshin say that they are so cash-strapped that international finance must be provided to improve safety and stop pollution.

"We simply cannot afford to improve safety and stop pollution until we receive more investment, and that has to come from richer Western countries," he says.

And it is money that is at the root of the problem.

The livelihoods of thousands of people depends on ship-breaking, a job too dirty and too costly for the developed world.

It may be work that is underpaid and dangerous, but it remains the most cost-efficient way of disposing of the world's growing number of unwanted ships.