The governing body took the decision early this morning after analysis of the latest water samples.

It followed recent above-average rainfall in Paris, which had caused sewers to overflow and leading to the water quality in the Seine remaining below acceptable standards for safeguarding swimmers' health.

World Aquatics decided to cancel the event in consultation with public health authorities and event delivery partners.

"World Aquatics is disappointed that water quality in the Seine has resulted in the cancellation of the World Aquatics Open Water Swimming World Cup, but the health of our athletes must always be our top priority," said World Aquatics President Husain Al-Musallam.

"World Aquatics understands that further infrastructure projects will be completed to significantly improve water quality in the Seine in the lead-up to next year’s Olympic Games.

"World Aquatics remains excited at the prospect of city-centre Olympic racing for the world’s best open water swimmers next summer.

"Based on this weekend, it is clear that further work is needed with Paris 2024 and local authorities to ensure robust contingency plans are in place for next year."

Training on Friday (August 4) had already been cancelled and the women's race had been postponed from yesterday until today in the hope the water quality would improve.

Paris Mayor Anne Hidalgo has promised that the Olympics in the French capital will be the catalyst for a massive clean up that would lead to three new sites being opened in 2025 so that public swimming would be allowed in the Seine.

Authorities had banned swimming in the river in 1923 because of high levels of pollution, a problem stretching back to the 16th century when the bodies of those killed in religious wars between Protestants and Catholics were thrown into the water.

"Prior to and even during the recent rainy period in Paris, water quality in the Seine has regularly achieved the levels required for healthy public swimming, demonstrating the progress that continues to be made," Paris 2024 said in a statement following today's cancellation.

"In early July, swimmers took to the Seine at the Bras Marie, one of the three Paris city-centre sites earmarked for public swimming facilities from 2025.

"The improvement of the quality of the water has already been seen with the authorisation given on 27 July for the organisation of the events in the Seine. 

"This followed the favourable opinion issued by the Regional Health Agency in the light of the results of samples taken between 6 June and 19 July."

Open water swimming has been hit by pollution concerns at the last two Olympic Games.

At the end of the Tokyo 2020 test event in 2019, swimmers protested against the quality of the water in Tokyo Bay.

Before the 2016 Olympics in Rio de Janeiro, there was several months of controversy about the prospect of swimming in Guanabara Bay, where the water is heavily polluted with garbage and toxic waste.

The World Health Organization advised competitors to keep their mouths shut during the event.

Paris 2024 claimed they hoped that water quality will improve enough for the triathlon test event to take place in the Seine later this month.

"Water quality will continue to be monitored carefully, in the confident expectation - based on the current weather forecast - that elite athletes will compete in the Seine later this month, at the World Triathlon and Para Triathlon Test Event Paris scheduled for 17-20 August," French officials said in a statement.

"With a year to go before the Games, the efforts to make the Seine swimmable, led by the State and the City of Paris, continue to significantly improve the quality of the water in the Seine."