The cremated remains of babies were secretly buried after parents were led to believe there would be no ashes to scatter, it has emerged.
Child bereavement charity Sands Lothians said Mortonhall Crematorium in Edinburgh carried out the practice for 45 years, and that up to 4,500 families may have been affected.
The remains of children who were stillborn or days old were buried in the council-owned crematorium's Garden of Remembrance, without being offered to be returned to their parents.
The situation came to light when babies were cremated at two other crematoriums in the city, in Seafield and Warriston, and their families were given ashes to scatter afterwards. Edinburgh City Council has launched an investigation to "establish exactly what has gone on". It said families had been offered the remains of their babies from Mortonhall since May last year.
Dorothy Maitland, 57, operations manager of Sands Lothians, had her daughter Kaelen cremated at Mortonhall in 1986, and was told there would be no ashes to scatter.
She said: "The charity had, and still has I must add, a good relationship with Mortonhall, and we had no reason not to believe them. People were led to believe there would be no ashes to scatter from a baby. Questions started to be raised when parents who had their children cremated at the city's private crematoriums - Warriston and Seafield - were given their ashes.
"I thought, why are parents able to get them from there?" But I was actually led to believe that those two places were lying. Seafield and Warriston have been giving ashes for 17 years - even from very small babies. I took it up with Mortonhall, which now has a new manager. It turned out that the remains had been buried in the crematorium's Garden of Remembrance - but it is just a plain bit of grass.
"I felt this had to be shared with families who might have been affected - we couldn't just not tell them. It is a practice which took place for about 45 years and we believe there may be 4,500 families affected. In the last year, Mortonhall has been giving ashes, and it is under new management. None of the staff who would have been responsible for this still work there, but someone has to be held to account.
"We are holding a public meeting next week with affected parents and council representatives. The council is being led by us and has launched a formal investigation."
Law firm Thompsons Solicitors has opened a free helpline for families to seek legal advice, which can be contacted on 08000 810 072. Edinburgh City Council urged anyone with concerns to contact its dedicated phone line on 0131 200 2383.