Police have an unusual undercover surveillance job this week, scanning the ramps and observing models at Lakme Fashion Week to check that no one intentionally displays too much flesh.

Police in plain clothes mingled with the cigar-chomping, crystal-clinking class at the Lakme Fashion Week, after busting zippers and slipping bustiers at the show's last edition sparked a morality debate in the conservative country.

"We are keeping an eye on each show. We don't want any bad example to be set," said Sanjay Mohite, deputy commissioner of police in Mumbai.

In March, a series of "wardrobe malfunctions" at the show saw models exposing their breasts and buttocks, sending newspapers and television channels into a frenzy of excitement.

The police even launched an investigation into the incidents, but later concluded that the clothes had come undone by accident.

This time, police have issued a 28-point guide for the organisers and designers, including a directive that models wear nipple tape so that they don't show through flimsy dresses, and that lights be switched off if clothes come off.

Police said they reserved the right to cancel a show if their guidelines were violated.

"We have a set of guidelines to follow. I think everyone is happy about it," said Anil Chopra, vice-president of organisers Lakme.

The Lakme Fashion Week, which ends on Saturday, is being attended by top buyers such as Browns, H&M and Saks Fifth Avenue, and is parading the creations by 47 young or famous designers.

Talk of sex in public is considered rude in India, while even holding hands or kissing in public is frowned upon and can draw jeers.

Officials even declared war on Mumbai's traditionally risque nightlife last year, shutting hundreds of popular dance bars on the grounds they bred crime and prostitution.

Some hardline Hindu groups are part of a growing band of cultural vigilantes opposed to what they see as increasing mimicry of the West, especially by teenagers.

Such groups have in the past stopped young people from celebrating Valentine's Day and prevented the screening of controversial films dealing with homosexuality, saying they denigrated the ancient traditions.