Korea Exchange said on Monday it will hold a briefing at its Yeouido headquarters in Seoul for officials from all member firms.

The exchange said the session will share details including measures to improve rules and information technology development work linked to the launch of pre- and after-market trading. It will also hold a question-and-answer session.

The exchange has announced it will introduce a pre-market session for before-hours trading and an after-market session for after-hours trading from June. It said it expects investors' trading opportunities to expand sharply.

Under the exchange's plan, the pre-market will run from 7 a.m. to 8 a.m. and the after-market from 4 p.m. to 8 p.m., extending total daily trading hours to 12.

But opposition from the industry is strong. The Securities Industry Headquarters of the National Office Financial Services Union held a news conference on Jan. 22 in front of Korea Exchange in Yeouido and called for an immediate withdrawal, saying, "Extending trading hours is not financial advancement but a path to mutual ruin."

The union said the exchange's extension plan would forcibly spread limited liquidity into early morning and night hours, creating quote gaps and increasing the risk of price manipulation.

It also criticised the plan, saying forcing early-morning starts and night work could sharply raise labour intensity not only for sales staff but also for essential head-office personnel in IT, settlement and funding, and could threaten the stability of the financial system.

In particular, the union said there was no meaningful effect in expanding liquidity even when trading hours were extended by 30 minutes under the Park Geun-hye administration, and criticised the exchange for pushing ahead unilaterally.

Some member firms are also complaining about the burden of system development and operating costs and difficulties in staffing, and a heated debate is expected at the briefing.