Isabella Rossellini, Jane Fonda and Gloria Steinem, among others, have been inspired by 50 is the New Fifty, a new book from Suzanne Braun Levine, founder and former editor of Ms, the ground-breaking feminist magazine.

Fonda called the book "useful, comforting and smart".

"The assumption is that youth - or at least younger - is the ideal state and that, given a choice, no woman in her right mind would relinquish it. I have found the opposite to be true," said Levine. "They say 50 is the new 30, as though they are getting a new lease on youth. That is not it at all."

Today she will be joined by Rossellini and Steinem in New York to discuss her book. "This honest and empowering book is the antidote to all those anti-ageing creams and glum pronouncements about life after 50," said Rossellini, who was fired as spokesperson for Lancome in 1995 soon after she turned 40 because managers considered she was too old. "This book explains why for me, and for so many other women, this has turned out to be the most free, creative and rewarding time of life."

Steinem became a spokesperson for ageing issues in 1974, on her 40th birthday, when a reporter said "Oh, you don't look 40", and Steinem famously replied: "This is what 40 looks like. We've been lying for so long, who would know?"

Levine said: "Fifty is an exciting new stage of life where women are feeling more comfortable, more masterful, more full of hope and energy than they felt in their 30s. I haven't met a single woman, truly, who would like to go back to her life when she was 30. We might like to go back to our lives when our bodies were a little different and we could wear belts, but otherwise, in terms of life experience, women are finding that their 50s, their 60s and even their 70s are a very exciting and authentic time.

"To listen to the society we live in, you would think that you have to stay young - and look young - to be happy. And we literally buy into that message, spending millions on age-defying cosmetics, surgery, drugs and making a book that promises to teach us 'How Not To Look Old' a bestseller," she said.

"We live in a society that is very ageist. Certainly the most significant victims have been women. Now we are creating a whole new age for women that really defies the stereotype that as women get older they should be invisible, they should sit by the phone and wait for an opportunity to babysit their grandchildren. I think our experience is going to change the perception of women in this society."

Steinem, author of Doing Sixty and Seventy, a book on age stereotyping and the unexpected liberation that comes with growing older, called Levine's book a battle cry. "No more pretended youth!" she said. "Suzanne shows us the wisdom and joys of living in our own personal present. For women who have been pressured into living the past over and over again, this book is the first true age liberation.

"If each of us stops trying to hide her chronological years, we will liberate the future for all of us," said Levine. "Susan Sarandon - who is in her 60s - is one of the sexiest-looking actresses around. Or Helen Mirren, 63, whose persona bespeaks maturity and whose bikini self impressed many of us a few months ago.

"Madonna, the one-woman reinvention operation, just turned 50. As she builds and hardens her body, she is looking a bit like an android, but she isn't hiding her age."

Mary Eileen Williams, founder of the feistysideoffifty website, said: "Without a doubt, there's a revolution going on and older women are leading the charge. We baby-boomers are known for spearheading sweeping social reforms, making news and breaking the mould for what is viewed as the 'typical' female experience. And we gals certainly aren't about to stop that now."