SHANGHAI (BLOOMBERG) - China's weakest stocks faced another blow after exchange regulators issued tougher rules to weed them out of the market.

More than a dozen firms under so-called special treatment status saw shares fall their 5 per cent limit in Shanghai and Shenzhen after draft revisions were issued late Monday (Dec 14) seeking to shorten the delisting process and toughen financial, trading and violation criteria. Companies under special treatment have received delisting warnings for reasons ranging from accounting issues to business failure, and they're subject to trading restrictions.

The broader market didn't show much reaction in China, with the CSI 300 Index down 0.4 per cent as of the midday break on Tuesday and the tech-heavy ChiNext Index rising 0.2 per cent.

The proposed revisions to delisting rules for all mainland firms are an acceleration in efforts by China to clean up the stock market and bolster investor confidence. Included in the draft is companies losing their listing if market capitalization finishes below 300 million yuan (S$61 million) for 20 straight days.

The draft comes after China Securities Journal reported last month that a government panel approved a delisting implementation plan, making it a top-level proposal.