More than a thousand marine turtles die every year after becoming entangled in rubbish in the oceans and on beaches, according to research.
The rise in plastic refuse in the ocean and on beaches is killing turtles of all species, with a disproportionate impact on hatchlings and young turtles.
A world-wide survey by the University of Exeter found that 91% of the entangled turtles were found dead.
They also suffered serious wounds from entanglement, leading to maiming, amputation or choking. Others that survived were forced to drag discarded rubbish or debris with them.
The survey found turtles are being tangled up in lost fishing nets, plastic twine and nylon fishing line, as well as six-pack rings from canned drinks, plastic packaging straps, plastic balloon string, kite string, plastic packaging and discarded anchor line and seismic cable.
Turtles were also discovered entangled in discarded plastic chairs, wooden crates, weather balloons and boat mooring line.
The research sheds light on the true threat of plastic pollution to marine turtles, which other research has shown also eat plastic rubbish and marine creatures caught up in it.
Professor Brendan Godley, the lead author, warned that as plastic pollution increases more turtles are likely to become entangled.
"Plastic rubbish in the oceans, including lost or discarded fishing gear which is not biodegradable, is a major threat to marine turtles," he said.
"We found, based on beach strandings, that more than 1,000 turtles are dying a year after becoming tangled up, but this is almost certainly a gross underestimate.
"Young turtles and hatchings are particularly vulnerable to entanglement. Experts we surveyed found that entanglement in plastic and other pollution could pose a long-term impact on the survival of some turtle populations and is a greater threat to them than oil spills.
"We need to cut the level of plastic waste and purse biodegradable alternatives if we are to tackle this grave threat to turtles’ welfare."
Turtle mortality from entanglement has increased substantially over the past century, as with marine mammals and birds.
The study found that 84% of the 106 experts surveyed on the Atlantic, Pacific Caribbean, Mediterranean and Indian ocean coasts who responded said they had found turtles tangled in rubbish, including plastic debris and lost or discarded fishing gear.
All species of turtle were found entangled, but olive ridley turtles are the most likely species to get tangled up. The species nests in the hundreds of thousands.
It forages in areas where marine debris can aggregate, and they may also be attracted to feeding on marine rubbish, including discarded fishing tackle.
Most entanglements recorded were in lost or discarded fishing gear known as ’ghost fishing’ rope, nets and lines.
Since the 1950s the fishing industry has replaced natural fibres such as cotton, jute and hemp with synthetic plastic materials such as nylon, polyethylene and polypropylene which doesn’t biodegrade in water.
Will McCallum, Greenpeace UK’s head of oceans, said: "The throwaway plastic we use for just minutes can turn into a floating trap for marine creatures like whales and turtles that lurks in our oceans for centuries.
"If UK ministers are truly feeling inspired after watching Blue Planet 2, then a good place to start would be stopping plastics getting into the ocean by pushing ahead with plans for a deposit return scheme.
"And if chief executives of major companies like Coca-Cola want to avoid being part of the problem then they need to start reducing their plastic footprint without delay."
Paul de Zylva, senior nature campaigner at Friends of the Earth, added: "It’s a tragedy that so many turtles die entangled in our plastic.
"If you see carelessly discarded plastic bags, bottles and packaging in the street it is likely that it will get washed or blown into rivers where it then reaches the seas to pose a lasting threat.
"It’s time to get drastic with plastic. We can all help by re-using bags, carrying a reusable water bottle and cutting down on plastic packaging."
The findings are published in the journal Endangered Species Research.