"The dignity of children is inviolable," association president Heinz Hilgers told the Kölner Stadt-Anzeiger on Tuesday, referring to the scandal which resulted last week in the resignations of SPD politician Sebastian Edathy and the former Agriculture Minister Hans-Peter Friedrich.
"It's a serious contravention of human rights when photos of children are sold or bought. They are never asked for their permission. That crosses a line," he said.
Hilgers demanded stricter rules on the sale of photos of children.
The association's calls found wider political support on Tuesday as the government fought to gain control over the child pornography scandal.
"The Edathy case clearly shows that there's a loophole in the law," the parliamentary commissioner for questions of child abuse Johannes-Wilhelm Rörig told Die Welt newspaper.
"When depictions of children are made to satisfy the sexual interests of adults, this has to be subject to criminal sanctions," he added.
Currently the law distinguishes between child pornography and images of naked children in which their genitals are not explicitly in focus. Taking and trading these images is not illegal under current laws.
"You can't punish it [buying and selling photos] in the same way as child pornography," added Hilgers. "There has to be a slight difference."
Yet the Edathy scandal has raised fears over posing photos - such as those alleged to have been found on the politician's computer. Posing photos typically show children fully clothed, partially clothed or naked where the context is not explicit but has possible sexual overtones.
"The mass distribution and commercial exploitation of so-called posing photos is an alarm signal," Hilgers' colleague Child Protection Association chairwoman Paula Honkanen-Schoberth told the Neue Osnabrücker Zeitung.
"You always have to consider that violence and child abuse are behind [these images]," she said.
But the chairwoman of the Bundestag’s Legal Committee, Renate Künast (Greens), said it would be difficult to implement a law around photos of naked children.
For example, photos of youngsters taken by their parents on the beach must not be criminalized, Künast told Deutschlandradio Kultur.