Researchers in the US say they have created an ultra-slippery toilet coating that could help save vast quantities of water around the world.

Scientists at Penn State University say the coating cuts the amount of water required to flush excrement by 90%.

They say it also prevents bacteria from building up in toilet bowls and reduces associated odours.

The spray, which is more slippery than Teflon, would be affected by urine and need reapplying after about 50 flushes.

Researchers hope that the discovery could help reduce water waste. Every day, more than 141 billion litres of water are used to flush toilets.

According to the researchers, who published their findings in the journal Nature Sustainability, the fresh water used to flush the world's toilets each day is six times Africa's total water consumption.

"Our team has developed a robust bio-inspired, liquid, sludge- and bacteria-repellent coating that can essentially make a toilet self-cleaning," Tak-Sing Wong, associate professor of mechanical engineering at the university, told Penn State News.

"Poop sticking to the toilet is not only unpleasant to users, but it also presents serious health concerns," he said. "Our goal is to bring impactful technology to the market so everyone can benefit," he added. BBC