SEOUL, May 27 -- Starbucks Korea's sales have taken a sharp hit after backlash over a promotional campaign accused of mocking one of South Korea's darkest chapters in modern history, according to new data reported by the Korea JoongAng Daily.

Figures released today showed the coffee chain's weekly payment volume plunged by more than 8 billion won (RM22 million) in the immediate aftermath of the controversy surrounding its "Tank Day" tumbler promotion.

Data from Mobile Index, operated by AI analytics firm IGAWorks, showed Starbucks Korea recorded 23.69 billion won in payment volume between May 18 and Sunday, down 26.3 per cent from the 32.16 billion won logged the previous week.

Compared with the week before that, spending was also down...