Grandmothers rally for release of children in detention in Melbourne CBD

Political agenda is overshadowing the urgent need to free asylum seeker children from detention, an Australian advocate group says.

Grandmothers Against Detention of Refugee Children have gathered in Melbourne to rally for the release of all asylum seeker children and their families, chanting "free the children" while walking through the CBD.

The group is also critical of the federal government's battle with human rights commission president Gillian Triggs after her report into children in immigration detention.

Clare Forbes, one of the groups's co-founders, says Professor Triggs recommendations, including the release of all asylum seeker children, must be implemented immediately.

"Vilifying Dr Triggs, the messenger, who criticised conditions under both Labor and coalition governments, must stop now," she told the crowd of grandmothers aged 40 to 90, who attended from around Victoria.

"Australia's reputation as a nation that cares about decency, justice and compassion is at stake."

The groups's chairwoman Dr Gwenda Davey said children were kept in detention for an average 400 days in Australia, compared with the UK's limit of 72 hours.

"We should free all these children and their families and welcome them into the Australian community," she said.