Authorities in Guangdong province are considering suspending mobile phone numbers if they are found sending more than 300 pornographic or spam text messages in an hour.

Gu Weizhong, director of the Guangdong Communications Administration, revealed the plan at a group discussion during the session of the Guangdong provincial political consultative conference.

Once the phone numbers are suspended, an investigation will be launched to determine whether any illegal acts are involved and if so, the numbers will be revoked, Gu said.

Responding to concerns that phone numbers might be suspended for sending isolated, private jokes following the latest move, Gu said the freedom of communications between phone users will be guaranteed and the authorities will be able to make distinctions between such messages and pornographic ones through "technological means".

The numbers previously suspended were all found to have been involved in illegal acts, he said.

In 2008, a similar regulation was implemented in Guangdong to intercept illegal or spam messages and blacklist the numbers involved.

Any such messaging is defined as illegal with limits of 300 such text messages in an hour, or 200 for a number of mobile network operators; or 1,000 of the messages sent a day; or 100 multimedia messages an hour or 500 a day. The limits are three times higher during holidays.

Apart from these limits on the number of messages, key word searches and analysis are also used to screen out illegal messages before results are evaluated and approved by the relevant authorities.

Phone numbers that have their messaging functions suspended are only able to resume with police approval.

"The hourly limit of 300 messages helps indicate that any suspicious activity goes beyond communication between friends and families, and some intervention may become necessary," said Liu Wei, a businessman in Guangzhou.

About 900,000 mobile phone numbers had their messaging functions suspended for sending out illegal or spam messages in Guangdong last year, said Yang Yuncai, director of the information safety division of the Guangdong Communications Administration.

"We do not rule out the possibility that some ordinary users had their accounts wrongfully suspended, but we have not received any complaints on that," Yang said earlier this month.

China Mobile in Beijing and Shanghai also threatened to suspend users over "illegal or unhealthy" content.