Actress Demi Moore in her upcoming tell-all memoir "Inside Out" reveals she regrets having threesomes with ex-husband Ashton Kutcher, who later used them as an excuse of infidelity.

The 56-year-old actress has dropped bombshells about her eight-year-long marriage with Ashton Kutcher and the reasons behind their separation in 2013.

Demi Moore said their relationship felt perfect when they met at a mutual friend's party in 2003, but trouble began after she miscarried their baby at six months, and fell into alcohol and drugs and their attempts at IVF also failed, reports Radar Online.

Moore said she and Kutcher had two threesomes to which she agreed only because she wanted to please Kutcher by engaging in the three-way sex, but regrets making the "mistake". "I wanted to show him how great and fun I could be," she wrote.

According to the report, Kutcher was filming a sex-drenched movie called "Spread" with actress Jennifer Jason Leigh and allegedly lied to his wife. The actress wasn't comfortable with Moore on set. Jason Leigh who later dropped out of the film had no issues with Moore.

"The bottom line was that she wasn't worried about me being on set, he was. He wasn't honest," Moore writes in the book.

The "Striptease" actress said she saw media reports about her husband cheating with a 21-year-old woman in their home. She claimed her husband wasn't entirely apologetic for infidelity and blamed their trysts with a third partner for his behaviour.

"Because we had brought a third party into our relationship, Ashton said, that blurred the lines and, to some extent, justified what he'd done," Moore wrote in "Inside Out".

The couple were still together working out their differences when Moore saw another news about Kutcher cheating with a young woman at his friend's bachelor party, that too on their sixth anniversary weekend. Moore said she felt sick to the stomach and knew the woman wasn't lying about the encounter.

In the memoir, the actress mentioned that Kutcher moved out of their home in 2011, and the couple officially got divorced two years later.

Ashton Kutcher and Demi Moore
Kutcher (L) and Moore in happier times Reuters

While the "No Strings Attached" actor didn't take much time to move on and married actress Mila Kunis in 2015, Moore has not publicly dated anyone since their split. Kutcher now also shares two children with Kunis.

"Inside Out" is set to be released on Tuesday.