For more than three decades it had been the skeleton in Joni Mitchell's cupboard...the secret she had kept from everyone but her closest family.

Not even her most heart-rending songs which so often disclose her deepest intimate feelings, provided a clue to the torment of a woman who had away her baby girl at birth and not seen her since.

So when 54-year-old Joni revealed last week that she was desperate to be reunited with her long-lost child, the relief she felt was overwhelming.

'Having a baby that nobody knew about has been playing on my mind for more than 30 years and it's been sheer hell,' says the singer, who is now pleading with her daughter to contact her.

'I'm just glad I've spoken about it at last because it means I've no skeletons in the closet anymore - I'm clean.

'But I still can't stop wondering what my daughter looks like. There's so much I need to tell her.'

Joni, who shot to stardom in the late Sixties with hits including Woodstock, Big Yellow Taxi and Both Sides Now, had the baby when she was a 22-year-old student.

And her decision to try to trace her undoubtedly stems from the knowledge that, after a miscarriage six years ago, she will never have another child.

As a friend says: 'Having a baby became a real need for Joni. But after the miscarriage she realised that the daughter she'd had adopted was the only one she'd ever have.'

Joni was plain Roberta Joan Anderson in 1965...and interested only in fleeing her middle-class life in a Canadian backwater to pursue fame and fortune.

So after becoming pregnant during her first year at Alberta College of Art in Calgary, she left college and headed for the bright lights of Toronto, where the child was born.

It was two years before Joni plucked up the courage to tell her parents about the birth and the adoption. And as Myrtle and William Anderson watched their only daughter grow from coffee-house folk singer to rock icon, the close-knit family vowed never to reveal the secret - not even to relatives.

So 84-year-old Myrtle was stunned last week when Joni went public. 'I don't like the world knowing about this,' she said at the family home in Saskatoon, Saskatchewan, where she lives with her husband, a retired air force officer.

'I knew the father. He often came by to the house - and I think he'd have married her if she'd been willing. But neither I nor Joni will reveal his name. He is married with a family and they know nothing of this child.'

After signing the adoption papers, Joni threw herself into Toronto's burgeoning coffee-house scene. A few months later she met American folk singer Chuck Mitchell...and within 36 hours they had decided to marry.

But the fate of the marriage, which lasted about two years, merely underlined Joni's astonishing ambition to succeed.

Chuck, 62, told last week how their relationship fell apart after they moved to Detroit and Joni was given a 'green card' to live and work in the US. 'A month after receiving her card she'd gone'.

Now remarried with two young children of his own, he says he is please that Joni has told of her desire to find her daughter. 'It's good for her to pay attention to the loose ends in her life, because she left a lot behind. But I don't think she regrets what she did - a baby would have got in her way.

'That's because she was very ambitious, very calculating and very self-centred - and so was I. She wanted to escape her Canadian upbringing and get on the big stage. She always knew what she wanted.

'I became excess baggage to her about six months after we go together. And it was really hard for me. I'd waited a long time to get married. This was it. 'I felt "What's wrong with me?" and had phases of resentment and anger. But gradually this faded.'

After Joni broke into their Detroit apartment and took exactly half of everything before heading for New York, Chuck changed the locks.

'She just turned up with a truck and a group of friends,' he said.

'When we split I told her that I wanted my name back. She just said that it was her name now.'

By the end of the Sixties, that name was known worldwide. And Joni's fame continued into the Seventies and albums such as Blue and Hissing of Summer Lawns.

She married session musician Larry Klein in 1982, but their attempts to start a family ended in miscarriage. The couple separated four years ago, although they are still friends.

Joni's parents were fond of Klein. 'We were very disappointed when it ended,' says Myrtle. 'But he had his own problems - he suffered depression. He was quite a bit younger than our daughter, but he was always very supportive. It was tough when Joni miscarried.'

If Joni is desperate to find her daughter while her parents are still alive, Myrtle is equally anxious now to meet her granddaughter.

The singer had to go public in her search for the girl because strict laws on adoption in Ontario - where she was living when she had the child - have frustrated all her attempts to discover her identity in the past two years.

The state will merely allow parents who gave up a child to place their names on a register of those seeking contact with their offspring. If Joni's daughter asks about her mother, the two will be put in touch - but not otherwise.

'I can't believe how difficult it's been to trace her,' says Joni. 'The people holding the papers simply refused to help.

'I had a different name all those years ago, so she may even know the name but not realise who I am. I don't want to cause her any problems, but I'm just desperate to meet her.'

Myrtle added: 'Joni went right back to the source. She went to the hospital and the people who dealt with it. But she couldn't get anywhere.

'OK, the law is intended to protect the adoptive parents. A lot of them resent anyone turning up.

'My only fear is that Joni doesn't get a lot of people coming out claiming they are her daughter now.'

Then, poignantly, Myrtle lets slip something millions off fans never realised... that her daughter did, in fact reveal her sorrow over her lost child.

In one verse of Green, a song on her 1971 album Blue, Joni laments:

Child with a child pretending
Weary of lies you are sending home
So you sign all the papers in the family name
You're sad and you're sorry, but you're not ashamed
Little Green, have a happy ending.

Whether there is to be a happy for Joni - and a 32-year-old woman somewhere in North America who has never known her real mother - only time will tell.