May 16 (Reuters) - French video game producer Ubisoft (UBIP.PA) posted the biggest operating loss in company's history on Tuesday but stuck to its guidance for the current financial year, citing a renewed focus on blockbuster titles. The maker of the hit "Rainbow Six" franchise posted a full-year non-IFRS operating loss of 500.2 million euros ($550.6 million), in line with a target announced in its January profit warning. The family-run firm has been dogged by game cancellations and delays in recent years, booking a writedown estimate of around 500 million euros in 2022 due to research and development expenses. The Paris-listed publisher confirmed its estimate for a full-year core profit of around 400 million euros, while forecasting first-quarter net bookings of around 240 million euros. ($1 = 0.9084 euros)Reporting by Victor Goury-Laffont and Enrico Sciacovelli; Editing by Jan HarveyOur Standards: The Thomson Reuters Trust Principles.

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