"It was kind of like a weight, I felt a pressure on my thighs. At the same time physical breath, and stroking," she explained.
Asked by a curious Holly Willoughby whether the encounter led to an orgasm, she said: "Yes, for me."
Amethyst's fiance discovered she was "cheating" when the ghost apparently showed its physical form to him, something which she herself had never seen.
"I think it was in love with me too and it wanted me to end the relationship," she told Holly and her co-host Phillip Schofield during the interview.
Amethyst, who says she now has "no interest in men", revealed she is hoping to find a special ghost to settle down with after dating several spirits over the past ten years.
A stunned Phillip and Holly wondered how the spiritual guidance counsellor could tell her ghostly "lovers" apart.
"You can always feel the difference, it's the same with different humans, they have different energies," she said.
Phillip then quipped: "Once you go ghost you never go back..."
Amethyst appeared unconcerned by the impact of her lifestyle choice on the possibility of starting a family, and said there was a chance she could have a phantom pregnancy with a spirit.
"That would be a unique thing to see a ghost baby, it would be like Casper," Phillip said.
Amethyst says her relationship with her first ghost lasted for three years before eventually petering out.
Since then, she says she's had 20 ghostly lovers - and is more embarrassed by her tally than the fact her partners don't take human form.
WHAT SCIENCE SAYS
Christopher French, professor of psychology at Goldsmiths College, University of London, and co-author of Anomalistic Psychology: Exploring Paranormal Belief And Experience says that ghostly experiences are not anything to do with mental illness.
"We need to avoid any kind of simplistic notion that anyone who has weird experiences is suffering from a mental illness.
"What is generally accepted is that hallucinatory experiences are much more common in the non-clinical, totally well-functioning part of the population than was once appreciated. Anyone can have hallucinations — particularly if you are stressed or sleep-deprived."
Professor French believes that most cases of 'sex with ghosts' can be explained easily.
"Sleep paralysis is common — 20 to 40 per cent of people say they've experienced it — and is the state between sleep and wakefulness when you realise you can't move. In a smaller percentage of the population, you get associated symptoms that can be very scary. One that's commonly reported is a sense of a presence — something or someone in the room with you.
"You can also get hallucinations where you see dark shadows or monstrous figures, you can get auditory hallucinations — you hear voices, footsteps — and also tactile hallucinations.
"You can feel as if you're being held, you might feel as if someone is breathing on the back of your neck, you can feel as if you're being dragged out of the bed.
"During a normal night's sleep, you go through different stages and it's REM sleep that's associated with vivid dreams."
