A plate of fish and chips is increasingly likely to expose people to untreatable bacteria because of the spread of superbugs at sea, new research has found.

A study of dolphins revealed a surge in antibiotic-resistant bugs that are dangerous to humans in the marine environment in just a handful of years.

While the mammals themselves are eaten in very few parts of the world, they are considered a good indicator for the safety of sea life that does end up as food.

Investigators at Florida Atlantic University periodically captured, swabbed then released Bottlenose dolphins from 2003 to 2015 in the Indian River Lagoon on the US Atlantic Coast.

They found that between 2009 and 2015 resistance to common antibiotics in various strains of E. coli more than doubled.

Meanwhile the resistance to drugs of a pathogen called Vibrio alginolyticus, known to cause serious seafood poisoning, also showed a significant increase.

Scientists also found evidence of resistant Acinetobacter baumannii, which is traditionally the cause of serious hospital-acquired infections.

Published in the journal Aquatic Mammals, the findings raise the prospect that diners of raw or undercooked fish could fall ill with bugs for which there are no useful medicines.

It comes days after Public Health England revealed there have been 19 new drug-resistant types of bacteria discovered in the UK over the past 10 years.