Euronext says case yet to be made for shortening trading day

LONDON, Feb 12 (Reuters) - The rationale for a "London" proposal to shorten Europe's share trading day has yet to be made, pan-European exchange Euronext boss Stephane Boujnah said on Wednesday.

Asset managers and banks have called for a year-long trial of a shorter trading day to improve liquidity, help attract more women into the sector with more family-friendly working hours, and improve the mental health of traders generally.

The London Stock Exchange has already held a public consultation on shortening the trading day, but has said that backing from major bourses across Europe would be needed to cut hours.

Euronext, which operates markets in France, Ireland, the Netherlands, Belgium, Norway and Portugal, is due to open its own public consultation on trading hours next month before reaching a conclusion.

"We will come with an opinion to comment on whether the proposal that has been put forward mainly out of London is relevant for continental Europe and Irish markets, or is more of a local idea," Boujnah told reporters.

"Frankly at this moment, I don't know."

Analysis was needed on the short and long term impact of such a change, in particular on retail investors, Boujnah said.

"Is there a next step following that one? What does it mean in price formation?" Boujnah said.

Britain's departure from the European Union last month has raised questions about the cohesiveness of pan-European stock markets once the UK's standstill transition period ends in December.

London-based share trading platforms CBOE, Aquis Exchange and the LSE itself have opened units in Amsterdam and Paris to trade euro shares if need be, thereby fragmenting trading.

(Reporting by Huw Jones, Editing by William Maclean)