'Before the unification, we had all kinds of police passes in all provinces because it was up to each province to decide the style. Some were horizontal, some were vertical,' Mr Fan said.

'While they are handling inter-provincial cases, sometimes they are asked by local police to provide further proof of their identity because the locals do not know if the credentials are authentic or fake.'

Ministry data suggested that in 2004, mainland police caught 11,846 suspects in murder cases that crossed provincial or county jurisdictions, up nearly 80 per cent from the previous year.

Mr Fan said the lack of a uniform police ID also posed problems for the public.

'The different styles also made it difficult for ordinary people to discern whether a police identity badge was genuine,' he said.

'With China's further opening and more frequent co-operation with international police, China does need a better regulated and unified appearance.'

The new pass will list an officer's name, gender, birth date, title, police rank, blood type and the certificate's validity period. The ministry official said the pass would also incorporate hi-tech features to make forgery difficult.

The most recent high-profile case of criminals using forged police passes involved a gang of four men who knocked on doors in residential areas of Hangzhou , Ningbo and other cities in Zhejiang in February, robbing four families of thousands of yuan.

'We are police. Open your door,' the robbers said, presenting fake IDs before brandishing guns, knives and handcuffs.

Under the mainland's criminal law, forging, selling or stealing a police pass can result in up to 10 years in prison.