BEIJING -- The Shanghai Stock Exchange on Friday unveiled a draft guideline narrowing price fluctuation limits for shares under delisting procedures to curb excess speculation and better protect investors.

As part of arrangements to speed up and simplify the delisting rules, the Shanghai Stock Exchange is asking for public feedback on the planned adjustments.

According to the proposed adjustments, listed companies operating at losses for two consecutive years will be labeled "under special treatment" ("ST shares") and those operating at losses for three consecutive years will be marked "*ST shares," and both "ST" and "*ST" companies face delisting to warn investors of the potential risks in trading such shares.

Among the proposed changes, the daily price upper limit of those "ST shares" will be adjusted to 1 percent, while the price down limit will be narrowed to 5 percent.

For those junk shares of which the closing prices are below 0.5 yuan (about 8 US cents) per share, the daily price upper limit will be adjusted to 2 percent in the A-share markets, while for those penny shares whose closing prices are below 5 US cents in the B-share markets, the upper limit will be capped at 20 percent.

On the risk warning board, the daily price up/down limit for "*ST" shares that are under delisting procedures will remain unchanged at 10 percent -- the same as ordinary shares.

"*ST" companies under delisting procedures will be delisted after being traded on the risk warning board for 30 trading days.

The stock exchange can further adjust the daily price ceilings with the approval of the China Securities Regulatory Commission, the bourse said in the guideline.

The stock exchange can suspend the trading of a company if 30 percent or more of its shares change hands in a single trading day.

During each trading day, an investor can buy a maximum of 500,000 shares of an "ST" or "*ST" company each, according to the proposed guideline.

China's two stock exchanges, in Shanghai and Shenzhen, announced measures in May this year to make it easier to delist companies in order to better protect investor interests.

According to the measures, companies with negative net assets for two consecutive years, those censured by the exchange three times during a three-year period, those whose shares closed below an established minimum value for 20 consecutive days or those whose combined trading volumes have fallen below one million shares for 120 consecutive trading days would no longer remain listed.