Customers would then need to lodge an appeal with the police, and their account would be reinstated only if the message was deemed acceptable.

'If the public security bureau confirms the message in question does fall into the category of 'pornographic or obscene', then that user's mobile number will become invalidated permanently,' a Shanghai Mobile official said in the report.

Beijing Mobile confirmed yesterday that it planned to introduce a similar policy tomorrow, the Beijing Legal Evening News reported.

Sina.com.cn later reported that the company had issued a clarification, saying it would suspend phone users' messaging services, not freeze their numbers entirely.

None of the reports spelled out exactly what would constitute an 'obscene' message.

However, Xinmin Evening News reported last night that an official for Shanghai Mobile had issued a denial of plans to invalidate numbers.

The brief article consisted of a repetition of the earlier news report with a one-line retraction attributed to an unidentified official branding the Eastday.com report 'inconsistent with the facts'.

The official denied the company had said mobile phone numbers would be invalidated permanently.

It is common for state-owned enterprises to announce proposals directly through official media outlets, particularly for government-backed initiatives. However, subsequent retractions are highly unusual.

Adding to the confusion, Eastday was continuing to publish the original news item among its top stories last night.

Shanghai Mobile could not be reached for comment yesterday, but a Hong-Kong-based spokeswoman for the parent company, China Mobile, said she understood that the retraction was genuine.

Mainland authorities have launched a campaign to clean up mobile networks and purge them of pornographic materials.

In contrast to the strict controls of internet content, the 3G mobile network has remained relatively free of restrictions - leading to criticisms that it has become a haven for indecent material.

The announcement of curbs on racy text messages was reported as being part of a 'second phase' of the campaign launched on Friday by the Ministry of Industry and Information Technology.

But the news has been met with an angry response from internet users, who almost universally condemned it as a step too far for government intervention.

'They can check up on what messages ordinary people are sending any time at all. That's just too scary!' one anonymous commentator said in a post on Eastday.com.

Others contrasted the efforts to spy on private messages with the lack of action against junk advertising messages or identity theft scams - both commonly sent out as blanket messages.

'Why can't they focus their energy on getting rid of those hateful con-merchants' text messages?' another frustrated reader of Eastday.com wrote on the website.