Executives at BDFM - the publisher of Business Day and the Financial Mail - and Sake said they were concerned the rules would affect transparency and accountability by listed firms.
The rules are expected to take effect in January and will apply to companies listed on the JSE and the junior AltX board.
Companies in countries such as the UK are not compelled to publish their full results in the financial media, and can publish only a summarised version with salient points such as headline earnings and dividends.
The JSE said listed companies would not be compelled to publish their entire results and they could also publish them in the newspaper of their choice.
The JSE's director of issuer services, John Burke, said the changes had been under consideration for the past 12 years, meaning media companies had had enough time to change their business models.
"There are companies who want the rule to go totally. It is about the choice (and) the executives want the choice," Burke said on Sunday.
He said that while the JSE understood the changes would affect the media sector, it could not publish regulations to sustain any company.
The JSE said it would not prescribe the content of short-form announcements (except interim reports and provisional annual financial statements) or approve announcements before they were published.
Ainsley Moos, editor-in-chief and publisher of Sake, which appears in Rapport, Beeld and Die Burger and has a combined readership of 700 000, said the proposals would undermine accountability.
"It is important to note that these are proposed changes and that there is a period of consultation that starts now," he said.
"Publishing the financial results is important for transparency and more so in newspapers as newspapers still play a significant role in an open society.
The international trend is to disclose more company information, not less," said Moos.
He did not want to speculate on the financial effect of the changed rules.
"It is at this stage difficult to say how these changes will affect a publication like Sake24," Moos said.
"But it is important to note that according to AMPS data, Afrikaans-speaking investors make up some 25% of all investors on the JSE and the majority of investors still view newspapers as a main source of this type of information."
Mzi Malunga, MD of BDFM, said the announcement could not have come at a worse time for media companies, which were still recovering from the effects of the last recession on advertising expenditure.
"It obviously will affect our business (but) it is difficult to estimate what the monetary affect will be, as we don't know which companies will react. It is likely to be significant," Malunga said.
"Whatever the JSE does, it should not be at the expense of vibrant financial media and at the expense of transparency," he said.
The proposed rules are available on the JSE's website and submissions can be made until June 29.
Source: Business Day via I-Net Bridge
