Ageless TV beauty Joan Collins has revealed the secret of looking sensational in your 60s — sex!

The glamorous granny — who turns 70 next May — insists: “Sex is preferable to a workout at the gym!

“It’s one of the best and cheapest beauty treatments for women.”

The former “Dynasty” vixen notes, “Many women find as they get older, or after they’ve had babies, their interest in sex decreases — and of course, the more the woman goes off sex, the more her partner will, too.”

And that’s tragic, believes Joan. “Older women can be sexy, beautiful and fit.

“Today 50 is almost the new 35 — and being in your 60s is comparable to how being in your 40s used to be.”

Joan covers sex and a whole range of other topics designed to help women attain her ageless beauty in her fascinating new book “Joan’s Way: Looking Good, Feeling Great” published by Robson Books.

The sexy star — who’s been married five times and has three children — insists: “Sex should be as natural and healthy a part of your life as eating and drinking. As you get older, you have more time for sex.

“We don’t stop sexual activity because we grow old. We grow old because we stop sexual activity. And it’s quality, not quantity that counts.

“Women need tender loving care, romance and love, and those who say they don’t are denying their femininity.

“Sexual interest and activity keep the adrenal and sex glands producing hormones which keeps us young by stimulating and enhancing practically all the body’s vital functions.”

In addition to maintaining an active sex life, Joan has other key tips for looking great — including avoiding jogging. “I’m strongly against jogging for women,” reveals the performer, who cautions it can lead to joint and cartilage wear and droopy breasts.

“And I’m not keen on going to the gym. So I exercise on my bedroom floor for 25 to 45 minutes several times a week.”

To stay curvy, Joan advises that you eat three meals a day, but cut out snacks.

Avoid fried foods and anything made from refined white flour or white sugar.

Drink a large glass of water before each meal — you’ll fill up faster and eat less.

As you look better and better, you’ll also feel the improvement, promises the actress.

“A person is as young as they look and feel,” she told an interviewer.

“The date on a person’s birth certificate is not always the best measure of their age.

“Whenever I see my age in print, I subconsciously think, ‘That can’t be right!'”