The plan is said to have been prompted by Shanghai-listed Shanghai Dazhong Taxi Co, which took the lead in releasing its results simultaneously in Shanghai and Hongkong at the weekend.

Shanghai Dazhong chairman Yang Quoping said the Shanghai stock exchange had resolved that every Shanghai-listed firm with A and B shares would be required to follow in the taxi company's footsteps.

No announcement of such a move has been made by the exchange.

''We believe in the importance of releasing simultaneously a listed company's information such as annual results, and so does the Shanghai stock exchange,'' Mr Yang said.

''We've also heard of mounting complaints about mainland firms revealing their accounts to A and B shareholders at different times.'' Criticism has been levelled at mainland-listed firms who have delayed issuing results to B shareholders.

This puts foreign shareholders at a disadvantage and may deter overseas investment in China stocks.

The Shanghai exchange, in its latest bid to rid itself of its image as a fledgeling securities market, is set to draw up guidelines aimed at improving the way companies listed there report results.

Guidelines have already been drawn up on dividend payouts of Shanghai-listed companies and the notification period for companies' annual meetings.

Mr Yang said the exchange had resolved that all Shanghai-listed firms with A and B shares would be required to consult overseas securities advisers before making dividend proposals.

He said this was to ensure that companies would not pay out their entire profits in dividends and bonuses, and that a reasonable amount would be retained in reserves for development.

There have been reports of Shanghai-listed firms being told to resubmit their bonus payout proposals because they were considered to be too generous and against the interests of the state.

Overseas investors have been baffled by bonus proposals because a substantial increase in the number of shares would dilute investors' holdings and reduce earnings per share.

Mr Yang said there was a plan to make companies give shareholders 20 days' notice of the annual meeting.

At the moment there is no strict requirement for notice to be given.

Mr Yang said that, under the new guidelines, the overseas underwriters of the original B issue would be responsible for notifying B shareholders.

The Shanghai authorities are also holding a weekly briefing, either on Friday or Saturday, on latest developments at the exchange.

Listed companies will also have the chance to release information to the media during the meeting.

Two such weekly meetings have been held by the authorities so far.