Authorities are warning Londoners over the health risks and other dangers of swimming in the Thames after it was revealed more than half of residents in the city would swim in the river.

That's despite millions of tonnes of sewage entering the river each year and a number of other risks to swimmers including tides and dangerously strong currents.

The figures come from a new survey of over 1,000 Londoners, most of whom said they would be willing to take a plunge in the river despite its myriad dangers.

The poll showed that 55 per cent think the river, or at least parts of it, is safe to swim in, while over a fifth (21 per cent) would rather swim in the Thames than a public pool in light of the current coronavirus pandemic.

Further, 45 per cent of city dwellers would be happy to swim in the river to cool off during the current heatwave, the survey found.

Wimbledon Times: 39 million tonnes of sewage is still flowing into the river each year. Image: Matt Alexander/PA Wire 39 million tonnes of sewage is still flowing into the river each year. Image: Matt Alexander/PA Wire

Former Love Island contestant and engineer Wes Nelson teamed up with Tideway, the company building a "super sewer" under London to help clean up the Thames, to urge people not to be tempted to take a dip in the river.

"Swimming in the Thames is dangerous on so many levels," he said, urging residents not to take the plunge.

"It's not just the sewage people should be aware of, but the tides, currents and water traffic too.

"The RNLI's two busiest lifeboat stations aren't on the coast - they're on the Thames, rescuing people from the water in central London."

Around four-fifths of those questioned in the survey (81 per cent) said up to a million tonnes of sewage is entering the river each year.

The real figure is in fact much higher.

Though the river is in much better shape than it was in the 1950s, when it was declared "biologically dead" due to pollution, 39 million tonnes of sewage is still flowing into the river each year before work on the super sewer started.

London's Victorian drainage system - built for a much smaller population in the capital than today's nearly nine million residents - regularly overflows, with untreated sewage spilling into the Thames, Tideway said.

The current pollution in the river does not only put people's health at risk if they swim in the water, but also harms wildlife.

Kayla Browne, apprentice civil engineer at Tideway's Carnwath Road site in Fulham, south-west London, said: "If you're considering swimming in the river, don't do it. Think about what you put down your toilet - that is essentially what you'd be swimming in.

"It may be hard to believe, but, until the tunnel is built, we're treating the river like a toilet.

"Sewage flows directly into the Thames when it rains, as this is the only way to stop homes and streets from flooding when the existing Victorian sewers overflow."