"ISI quality mark has been withdrawn with immediate effect from the bottled water plant of Varun Aqua Industries in Delhi's Khanpur area after tests revealed their samples are  not up to the existing standards," BIS sources told PTI.

This takes the number of plants facing such action to 12 in less than a month as earlier inspections by Bureau of Indian Standards had led to action against 11 plants including one each of PepsiCo, and Ion-Exchange and two of  Bisleri while a unit of Coca Cola was let off with a warning.

Varun Aqua Industries has been asked to stop using ISI mark after its samples fail to pass the microbiological tests, they said.

Licence withdrawal or cancellation of a unit automatically debars it from manufacturing bottled water since ISI Standard Mark is mandatory under government rules.

Action is part of an ongoing nationwide exercise under directive of Consumer Affairs Minister Sharad Yadav and would continue in the coming days, they said adding with samples having been collected from hundreds of companies, more licence cancellations are in the offing.

They said far from adhering to the proposed revised quality norms, a number of bottled water plants are unable to meet even the existing BIS standards forcing the bureau to take stringent action against them.

Yadav is scheduled to respond to a calling attention motion in Parliament on the controversy on Thursday.