Under the Japan Securities Dealers Association's (JSDA) guidelines, analysts at brokerages will be banned from gathering information that could reveal earnings results. Brokerages will also have to vet data gathered by analysts and ensure undisclosed material information isn't passed to clients.

But new punishments will not be brought in for breaking the guidelines, which could come into effect as early as October. Violations will instead be dealt with under existing rules on the treatment of material information.

At present, individuals who break the rules can be sacked or disbarred from the industry, while brokerages can be fined or slapped with punishments such as business improvement orders, the JSDA said.

Investors' access to non-public material information, such as earnings results, has come into focus in Japan in recent months.

The country's financial regulator censured local securities units of Deutsche Bank and Credit Suisse Group AG in December and April respectively for leaking earnings information to clients.

But Japan, the world's third-largest economy, lacks rules on so-called fair disclosure. In the United States, financial regulators brought in regulations to tackle selective disclosure of information by public companies in 2000.

The Financial Services Agency is considering bringing in fair disclosure rules - a possibility welcomed by corporate governance experts, despite a lack of clarity on when, and in what form, such rules could be introduced.

"Any focus in this system on how companies disclose what information to whom is a good thing," said Nicholas Benes, corporate governance advocate and representative director of the Board Director Training Institute of Japan.

The shifts come as Japan Inc - long criticized for neglecting shareholders - is being pushed by Prime Minister Shinzo Abe to improve corporate governance.

But the prospect of tighter rules has raised fears that Japanese firms will revert to reluctance in engagement with the market, potentially stifling the emergence of a more open relationship between corporate Japan and investors.

"It should be made very clear that companies cannot use this as an excuse not to meet with analysts, investors and the media," said Jamie Allen, secretary general of the Asian Corporate Governance Association.

(Reporting by Thomas Wilson and Emi Emoto; Editing by Adrian Croft)

By Thomas Wilson and Emi Emoto