On social media, Ms Coffey O’Brien said the event at 1pm on Saturday is intended to honour those buried in the former institution's children's burial ground and to ensure “they are not forgotten”.

Ms O’Gorman's daughter Evelyn died at Bessborough and is believed to be buried there, but there are no burial records for the children on the grounds, and only one grave of a child has been located following an examination of a section of land there.

In an invitation issued ahead of the vigil, Ms Coffey O'Brien stressed that the event is intended as an act of remembrance rather than a political statement.

"We have never been political and we do not want this politicised," she said. "This is about the babies and the girls who are buried in the children's burial ground at Bessborough."

She said the purpose of the gathering is to acknowledge the lives of those who died, regardless of how short their lives may have been.

Campaigners have long called for the children's burial ground to be formally marked, preserved and protected. Ms Coffey O'Brien said this remains their central objective.

"That's all," she said. "All lives must be equal in death."

Bessborough was one of Ireland's largest mother and baby institutions and recorded one of the highest infant mortality rates in the country.

Survivors and relatives have campaigned for many years for greater recognition of those who died there and for protection of the burial site.

Carmel Cantwell's brother William died at Bessborough but his grave cannot be located. She is part of a campaign to stop the development of 140 units being built there after the city council gave developers the green light.

Organisers of Saturday’s vigil say members of the public are welcome to attend in a "spirit of respect and reflection".

Meanwhile, Carmel Cantwell, who is behind the Bessborough Mother and Baby Home Support Group, is holding the annual Bessborough commemoration at the folly on the grounds of the former institution on Sunday, June 28.

The group is also opposed to the development of 140 units that recently got the green light from Cork City Council.

Singer Camille O’Sullivan will perform on the day, and speakers include the Lord Mayor Damian Boylan and survivor Noelle Browne, as well as guests from the US and the UK.