The chief of Lotte Chemical Corp., the chemicals maker of retail giant Lotte, was summoned by prosecutors Thursday to face questioning over a string of irregularities, including alleged tax corruption.

Huh Soo-young appeared before the Seoul Central District Prosecutors' Office over allegations of lobbying the local tax authorities and engaging in the company's unlawful suit against the government.

"I will fully cooperate with the prosecution," he told reporters before entering the prosecutors' office.

The 65-year-old, who has been leading the company since 2012, denied allegations that the group chairman Shin Dong-bin was involved in the process.

KP Chemical Corp., a subsidiary of Lotte, which later turned into Lotte Chemical, is suspected of filing a suit against the government in 2006 with doctored accounting records and getting some 27 billion won ($24 million) in tax refunds.

The company is also suspected of handing over some 20 billion won in illegal commission fees to Lotte Bussan Co. in Japan to create a slush fund containing billions of won.

Two weeks earlier, his predecessor Ki Joon was put in detention over alleged involvement in the corruption.

Prosecutors have been widening their investigation into the country's fifth-largest conglomerate after launching a full-fledged raid in June. (Yonhap)