Olivia Newton-John, best known for her starring role as Sandy in 1978 Hollywood musical movie Grease, is struggling with a sciatica health battle.

The 68-year-old Australian singer and actress – who survived breast cancer in 1992 and is an advocate for health awareness – has postponed her American concerts for the rest of May.

Australian publication New Idea report that her management were forced to hold off the performances due to Newton-John's worsening battle with the illness – a spinal and nerve condition that can cause numbness and weakness in the leg muscles.

An insider claimed that her condition has been debilitating, telling the publication: "So to see her unable to walk or get out of bed because the pain is so severe is incredibly rattling. We are very worried."

They also divulged that the tour cancellation was a big deal for Newton-John, who is known for her professionalism.

On 13 May, the official Olivia Newton-John Facebook page announced that the singer was sad to postpone some forthcoming shows.

It read: "I am disappointed too! We are rescheduling as soon as possible.

"I have had a long running issue with sciatica and I need to take this time to rest and deal with this very painful condition.

"My husband John is taking great care of me and I want to thank all my family, friends and fans for their concern, love, support and good."

The sciatic nerve is the longest nerve in the body and runs from the back of the pelvis, through the buttocks and all the way down both legs, ending at the feet. The pain of sciatica is usually felt in the buttocks and legs – and the pain can last for a year or more in some cases.

Meanwhile, Newton-John's daughter Chloe Lattanzi made headlines over the weekend for wearing an extremely low-cut dress on an Australian morning show in what has been described as a "train wreck interview".

The clip was posted on Twitter along with comments claiming she looked like a porn star and got a boob job for exposure as she lacked the skill and talent of her mother.

One social media user replied to the post with: "Sorry, can't help but laugh at this chick. What the hell has she done to herself, she looks like a porn star."

Another added: "I have no skill or talent unlike my mother so I'll go get a boob job and hopefully that'll give me some exposure. Singer / actor my arse."

While a third put: "Really??.what awful dress to wear on a morning show..."