Around the British Isles, killer whale numbers have halved to around 10 but could vanish completely - (C) www.audunrikardsen.com

Britain’s only killer whale pod will be wiped out by the end of the century because of deadly chemical pollution in the seas around the UK, a report has warned.

New analysis by an international team of researchers including the University of St Andrews and the Zoological Society of London has found that half of the world’s population of orca will vanish in the most heavily contaminated areas.

The chemical pollutants, polychlorinated biphenyls, or PCBs, were once widespread in paints, adhesives and electronics but were banned in the 1970s.

However the paint from old bridges, boats and buildings can still flake into the sea, or leach into waterways from disused mines where it was used as hydraulic oil or from landfill sites.

Around the British Isles, killer whale numbers have halved to around 10 because of the the chemicals and the mammals are likely to vanish altogether in the coming decades, the new research found.

Last May, a dead orca called Lulu was found washed up on the Hebridean Isle of Tiree with the highest levels of PCBs ever recorded and it is feared the rest of her pod will have the same level of contamination, which can impair the immune system and damage fertility.

View photos Wildlife charities are now calling on the government to include new measures in the new Environment Act Credit: Audun Rikardsen More

"This suggests that the efforts have not been effective enough to avoid the accumulation of PCBs in high trophic level species that live as long as the killer whale does, “ said Paul Jepson, Institute of Zoology, Zoological Society of London, England, who is another killer whale expert and co-author of the article.

Killer whales, because they sit at the top of the food chain, accumulate huge amounts of PCBs which have been ingested by animals further down.

The chemicals can also be passed down from mother orca to its offspring through the mother's fat-rich milk.

PCBs have been used around the world since the 1930s but following the 2004 Stockholm Convention, more than 90 countries agreed to have got rid of all use by 2028. Yet little is done to ensure companies are complying.

Wildlife charities are now calling on the government to include new measures in the new Environment Act to make the convention goals legally binding.

View photos Killer whales are vulnerable because they are at the top of the food chain More

Willie Mackenzie, Oceans Campaigner at Greenpeace UK, said: ‘‘Thirty years after they were banned, it’s staggering that polluting PCBs are not only still getting into our ocean, but that they are pushing our killer whales towards extinction.

Story continues