Authorities are introducing curbs on Shanghai-listed companies’ ability to halt trading of their own shares in moves aimed at preventing a repeat of actions during the summer crash — and which stand in stark contrast to easier-going rules in Hong Kong.

The Shanghai Stock Exchange plans to limit share suspensions due to asset restructuring to no longer than three months, with an additional two-month suspension permitted if circumstances warrant.

The draft rules come as the suspension of three mainland shipping groups in Hong Kong, for an expected state-sanctioned merger, passes that exact three-month mark without an update from the companies involved.

Shanghai’s proposals, which are open for comment until Friday, will allow a further two-month suspension permitted if circumstances warrant. Suspensions will not, however, be allowed to last more than five months.

The changes are aimed at stopping a repeat of early July when at the height of the Chinese stock market rout more than half of all listed companies suspended trading, purportedly due to “plans for major asset restructuring”. In reality, the suspensions were designed to prevent share price falls amid panic selling.

In addition to trapping investors during tumultuous trading, the mass suspensions played havoc with exchange traded funds that track broad indices, causing big discrepancies between the funds and their underlying assets.

“A lot of companies chose to suspend trading and some of these gave reasons that were quite vague,” said Guo Yanhong, an analyst at Founder Securities in Beijing. “I suspect the senior management of a lot of these companies were also shareholders and worried about falling stock prices.”

Mr Guo added that he believed the authorities also genuinely wanted to speed up mergers and restructuring.

Since the start of 2014, 13 per cent of Shanghai-listed companies that suspended trading in their shares citing asset restructuring did so for more than five months, the official China Securities News reported yesterday.

The Hong Kong-listed shares of three mainland shipping companies — China Cosco Holdings, China Shipping Container Lines and China Shipping Development have been suspended since August 10 pending news expected to involve a merger.

Asian bourses including Hong Kong and its mainland counterparts have typically been more amenable to share suspensions than are western markets such as London and New York, where suspensions are minimal and very brief.

The trading halts are a source of frustration to investors who have called for regulators to allow some form of grey-market trading. Hong Kong has few hard and fast rules to limit the length of suspensions, and as of the end of October, $46bn of equity in Hong Kong had been frozen for more than three months, up from $12bn in April.