Single Parent Action Group protest organiser Samantha Seymour said 730,000 children were living below the poverty line and that figure was set to rise.

Federal government welfare changes mean about 60,000 single parents have been moved onto the Newstart Allowance, losing between $60 and $100 per week in parenting payments.

"Effects of poverty include obesity, depression, suicide, developmental delays, poor schooling outcomes," Ms Seymour said on Tuesday.

Single mum Bianca Maciel Pizzorno, who attended the protest outside Parliament House, and said her twin boys, aged eight, had offered to empty their piggy banks to help pay the bills.

"It's hard to explain to an eight-year-old that $10 isn't going to help," she said.

"No is always the word these days."

Another single mother, Michelle Lee, said her eldest daughter had offered to drop out of school and get a full-time job.

"It's ridiculous that children feel they need to take on the role of a parent in a sole parent family," she said.

Australian Greens deputy leader Adam Bandt spoke at the rally of about 30 people, saying single mothers were being forced to choose between such things as paying the car registration or sending kids to school camp.

"Newstart is not enough to live on and it is certainly not enough to raise a child on, which is the most important job," he said.

Since January 1, single parents are no longer eligible for the parenting payment once their youngest child turns eight.

Instead, they are moved to the lower Newstart allowance of about $265 a week.

AAP