'We don't understand why this charge was introduced. In the eyes of rights lawyers, the only plausible explanation for introducing such a charge is to protect those with special status in China, those with money,' said women's rights lawyer Guo Jianmei.

'Years after its implementation, we see that this charge has damaged the rights of young girls, insulted them [by branding them prostitutes] and condoned the criminals. The charge must go.'

Under Chinese law, the charge of rape carries criminal sentences ranging from three year's imprisonment to death, while the new charge of 'paying for sex with under-age girls' is not punishable by death but only carries jail terms of between five to 15 years. An under-age girl is legally defined as a girl under 14.

And while having sex with a consenting girl under 14 in China is also considered rape, there is a condition that the man must know that the girl is a minor. And the charge becomes the lesser 'paying for sex with underage girls' once money changes hands, even if the man knew the girl was under-aged.

'How do you define payment? The girl could be lured into accepting the cash before the incident, or might be co-erced into accepting the money after the rape. Either way, they are too young to make such a decision,' Guo said.

This also highlighted an inherent conflict between the controversial charge and rape.

Guo added: 'If a minor is considered not having the legal mental capacity to consent to sex, then how could they be considered capable of understanding what prostitution means?'

Culturally, Chinese men prefer younger girls, and some men even believe that sleeping with young girls, especially virgins, would bring good luck. Guo said this also partly explained why such sex offences against young girls kept happening, and stronger legal sanctions were required against them.

Since 2009, when the first major case involving officials and underage girls broke in Guizhou , rights activists have persistently called for the abolishment of the charge. Many delegates supported this call during the country's annual parliamentary session, and even the state-run All China Women's Federation supported the call.

A commonly cited set of figures showed that in the five years from 2000 to 2004, the country's courts tried 176 cases of 'paying for sex with under-age girls' and sentenced 240 men, which equals to 48 a year. In 2009 alone, police arrested 175 suspects for the charge.

Women and children's rights professor Zhang Rongli said the charge was contrary to China's domestic and international obligations to put children's interest first when there was a conflict of interest.

'Here this charge clearly seeks to protect the right of an adult male before that of the young girl,' said Zhang, a law professor at China Women's University. 'And it even puts blame on the children.'

The reason for introducing the charge in the first place, Zhang said, was that some legislators or criminal law advisers to the government - mostly male - thought that it was unfair to charge a man with rape when he thought he was sleeping with a prostitute.

Legislators therefore believed that the controversial charge was already offering more protection to young girls, since a man is not criminally punished for seeking prostitution in China. So far there had been no response to the calls for abolishment of the charge, Zhang said, and this was probably because any change would have to wait for a new revision of the Criminal Code.

But authorities could still do something in the meantime to alleviate the harm of the clause, she urged.

'The Supreme People's Court has a duty to issue a guidance on how to strictly impose the clause,' Zhang said. 'There must be stricter definition on what constitutes prostitution.'