Japan is to outlaw the possession of child pornography, though the depiction of child sex abuse in manga comics and anime films is to remain legal.

The country's upper house of parliament is expected to pass legislation making possession of the material punishable by one year in jail.

Though production and distribution of child pornography has been illegal for 15 years, possession remains legal in a country described by the US State Department as "an international hub" for child pornography.

Activists applauded the reform, but questioned why it had taken so long to pass the law.

"As a member of a group that's been hearing the voice of the victims for many years, we welcome the news," said Shihoko Fujiwara, a representative of Lighthouse, a nonprofit group that helps exploited children. "Japan took so long, and it is too late to reach this decision as a developed country."

However, there are notable exemptions to the ban, with manga and anime child pornograophy still legal, and those in possession of the newly banned material given one year to dispose of it.

"The primary reason [for the new rule] is to protect the rights of real children," a lower house legislative official told Agence France-Presse. "Manga, anime and computer graphics are outside its scope."

However, representatives of the animation industry said that studies had uncovered no links between animation and paedophilia in Japan.

"The goal of the law itself is to protect children from crime," he said. "Banning such expression in animation under this law would not satisfy the goal of the law."

Japan is notorious not only for the material in its animations and comic books, including the "lolicon" ("Lolita complex") genre which features depictions of pre-pubescent girls, but for its "junior idol" genre of books and DVDs which features underage girls wearing skimpy clothing and posing provocatively.

A 2012 US State Department report showed a 9.7% rise in child pornography investigations from 2011, to a record of 1,596. Japan is the only country in the G7 group of the most developed nations where it is legal to depict sex crimes against children.