Fatbergs pose a threat to human health by acting as breeding grounds for superbugs immune to antibiotics, a new investigation has found.

Analysis of a 750-metre fatberg - a congealed mass of fat and discarded items - in a London sewer revealed strains of bacteria including E coli and listeria which are resistant to life-saving drugs.

Experts have warned that people could be exposed to the bugs in the event of a blockage which pushes sewage back up through domestic or commercial pipes.

In that event normal antibiotics could prove useless against the virulent strains.

Antimicrobial-resistance is one of the gravest current threats to global health, with experts estimating it could result in 10 million unnecessary deaths a year by 2050.

The study by Thames Water and Channel 4 also found significant evidence of prohibited gym supplements in the fatberg, including muscle-gain drugs banned by the World Anti-Doping Agency.

These made up a greater proportion of pharmaceutical traces discovered than illegal recreational drugs such as cocaine and MDMA.