Olivia Newton-John speaks out about "fracking"

Olivia Newton-John has spoken out on the issue of "fracking" - the process involves pumping a large volume of water mixed with sand and chemicals into rock to create frissures that allow trapped natural gas to be released.

In her open letter, Newton-John says she is "horrified to learn of the extensive plans for coal-seam gas and shale gas exploration in Australia".

"The public's awareness as to what is happening, and the potential consequences to our health and our land, shows that it's time for some serious inquiries," the singer wrote.

"Many of my friends and family were not even aware of what was going on until they heard from me," she said.

While there is a moratorium on fracking in NSW until the end of the year, the industry is set to become a significant contributor to the state's energy supply, with companies undertaking appraisals in Gunnedah and the Clarence-Moreton basins, home to Newton-John's Gaia Retreat.

The star is demanding to know evidence that coal-seam gas mining does not pollute drinking water, what chemicals are being used in fracking and why companies are exempt from revealing them.

"Until these questions are answered, I respectfully request a moratorium on the coal-seam gas exploration and mining in Australia until all risks have been fully explored," she said.

Read Olivia's Open Letter here.