The National Police Agency on Thursday released new guidelines for undercover investigators who use fake identification cards to apply for yami baito, or shady part-time jobs, in an effort to deter such crimes.

The NPA concluded that although such investigations involve the forgery of IDs, the practice is justifiable under the Penal Code and that they can be carried out under the current law.

The agency aims to introduce investigations in which undercover personnel use fake IDs as soon as implementation plans are formulated by prefectural police departments across the country.

According to the guidelines and other sources, investigations involving the use of fake IDs will target crimes such as robbery, special fraud, investment fraud and romance fraud, all of which have been frequently carried out by people applying for shady part-time jobs in recent years.

Only when asked by crime rings, the investigators will send them images of fake IDs, such as a driver's license or a My Number personal ID card, with names and photos that differ from their own.

The originals of the fake IDs will be stored in locked facilities to prevent them from being misused. Giving the originals to criminal groups or presenting them to third parties will be forbidden.

The undercover investigators will go to specified meeting places to round up or question perpetrators before crimes are committed.

Undercover investigations using fake IDs "will hopefully help prevent damage (from crimes), identify the instructor or ringleader and deter the recruitment of perpetrators," NPA Commissioner-General Yasuhiro Tsuyuki told a news conference Thursday.

In Japan, sting operations have been conducted against drug dealers. Unlike in those operations, investigators who conduct probes using fake IDs will not engage in infiltration operations or lead perpetrators to commit crimes.

Plans to create guidelines for undercover investigations using fake IDs and to swiftly introduce such operations were included in emergency measures compiled by the government in December last year amid a spate of cases linked to yami baito.