"Officers in charge of handling certificate-related affairs will also be punished for on-duty failings, including dereliction of duty and accepting bribes," he said.

In addition, some residents purchase fake identities in the slim hope that they will not be detected, "which must be avoided", he said.

"After all, there is a complicated social problem behind these small pieces of paper or card, such as the hukou," he said, adding that closing the gap between rural and urban hukou holders will take time.

In China, if a person spends their entire life working in a big city such as Beijing but does not have a permit to live there permanently, he or she can only collect their pension in the place where their household is registered. For rural residents that can result in a large loss of income.

Self-protection

Ruan conceded that although the rural-urban gap is gradually narrowing, there's still a long way to go: "In the short term, the problem must be reduced by stricter implementation of the law and by raising public awareness of self-protection."

A police officer surnamed Hu is responsible for household registration affairs in Shanghai. She said residents who wish to transfer their hukou must appear at the office in person and produce the relevant documents, including an ID card and a hukou certificate.

"If someone cannot show up, he or she must entrust the matter to another person whose identity has been verified by a third-party institute (brokers employed by members of the public to undertake administration of identity-related documentation)," Hu said.

She confirmed that public security departments do not update information relating to residents' hukou or ID unless a person applies to make an amendment, which is why some people do not realize that their ID cards or hukou certificates have been duplicated or even nullified.

She suggested that people should double-check the reputations of any third-party agencies with which they have dealings, and urged residents to think before handing over sensitive documents such as ID cards and hukou certificates to ascertain what they will be used for.

"People should also pay attention if this type of information is required by government departments and they make copies," she said.

Now, some businesses, including banks, are exploring the use of biometric information, such as fingerprints, to verify people's identities, which Hu said would be a good way of reducing the number of imposters.

For Ruan, the criminal lawyer, the problem lies in the wide gap between rural and urban areas in terms of the benefits provided by a residency certificate: "To eradicate the problem in the long run, we will have to narrow the gap between the urban and rural areas in many spheres, such as providing equal access to education and social benefits. Only then will the problem cease."

Contact the writers through caoyin@chinadaily.com.cn