The newly formed Bendigo chapter of Grandmothers Against Detention of Refugee Children demanded that children with their families be freed immediately into the community.

Protester Elizabeth Grounds said she attended the event not as a grandmother but as a human being.

Mrs Grounds said her years as a doctor had taught her a lot about the influences on children as they grew up.

She said a "lack of experience, lack of mixing with other people, lack of freedom or the knowledge of what freedom is, and bad memories" affected children in detention.

Co-founder of the Grandmothers Against Detention of Children in Melbourne Dr Gwenda Davey attended the Bendigo event. 

"I'm deeply distressed by what's being done to mothers and children," Dr Davey said.

"No other civilized country has such a policy.

"We're locking people up for years sometimes."

Dr Davey said the federal government's policies on the detention of children undermined Australian values of the 'fair go' and compassion. 

Bendigo group organiser Jan Govett said it was fitting the group protested by the fence surrounding St Paul's Cathedral because it was symbolic for the childrens' incarceration. 

In an address to the crowd, St Paul's Very Reverend John Roundhill said the detention of children was subverting the values Australians' wished to protect. 

"What is done in our name here and on our shores undermines our way of life," he said.

"We need to get back to what we should be - a country safe and welcoming for children."

To find out more about the Grandmothers Against Detention of Refugee Children in Bendigo, see their Facebook page here.