The only winners from the Prostitution Reform Act 2003 are men, says the National Council of Women of New Zealand.
Council national president Elizabeth Bang made the comment in light of sentences passed down to men convicted of having sex with girls under the age of 18.
She was alarmed at how light some of the sentences were.
The council supported the law change in order to validate and protect human rights - not to condone prostitution, she said.
"The law was meant to give protection to those over the age of 18.
"And along with that, was the belief that the reform would see prostitution practised only by those 18 and over, but we are still seeing girls as young as 13 and 14 on the streets selling their bodies."
The council was disturbed there appeared to be no disincentive for men for their actions when they were getting name suppression and light sentences for buying sexual services from underage girls, Mrs Bang said.
The council wanted to see tougher penalties applied to the Act.