The crackdown on pyjama-wearing in public has reminded many of a similar crackdown in Beijing - on the capital's hordes of topless males - ahead of the summer Olympics in 2008.

The Qiba neighbourhood in Shanghai's New Pudong district, only three bus stops from the World Expo site, has mobilised neighbourhood committee officials and volunteers since July to talk people out of the habit of wearing pyjamas in public.

The initiative has split public opinion. Some see pyjama-wearing in public as an embarrassment, while others view it as a tradition and a right.

China News Weekly quoted Qiba Neighbourhood Committee director Shen Guofang as saying it had started the campaign because it was worried that the sight of people parading about in their pyjamas could leave a bad impression among foreign visitors.

'We're the hosts. Even if a trivial matter goes before the public, it becomes huge and we can't let Shanghai lose face,' she said.

Dismissing the campaign as overkill, detractors even cited a collection of photos taken by a National Geographic photographer showing people wearing pyjamas in the street as a charming endorsement of the cultural phenomenon. Shanghai office worker Wang Shuai said choosing what to wear was a matter of personal liberty and nobody else's business, as long as it was not indecent.

'People are free to choose what they wear and you're are free to choose what you're looking at,' Wang said. 'If you don't like it, then try to ignore it.'

Wearing pyjamas as a fashion statement has its roots among wealthy social butterflies in 1930s Shanghai and the practice regained popularity in the late 80s.

But in recent years, the wearing of pyjamas in public has often been associated with elderly Shanghainese living in shanty neighbourhoods and the jobless, who have little incentive to dress up.

Shanghai Academy of Social Sciences sociologist Zhang Jiehai said wearing pyjamas in public started as a matter of practicality because people lived in cramped conditions with no clear line between public space and private place.

People then began to take the practice for granted. He said the tradition had outlived its usefulness and people should try to give it up because it was not hygienic, among other things. However he said the anti-pyjama drive was an attempt to whitewash Shanghai for the expo but there were better ways to achieve the desired result than ill-conceived government campaigns.

'If you want to tell someone how to do things, you should try to awaken the internal decency inside them,' Zhang said.