Tumblr rejected the requests of South Korean authorities to regulate adult content posted on its website, claiming it wasn't subject to Korean laws, a lawmaker has said.

The Korea Communications Standards Commission (KCSC), the country's content watchdog, sent 30,200 requests to internet service providers to delete posts related to prostitution and porn from January to June this year. Requests to Tumblr accounted for over two-thirds, totalling 22,468. By comparison, Twitter received 1,771, Instagram 12, and Facebook 5, data provided by MP Choi Myung-gil showed.

Last year the watchdog made 81,898 requests, with Tumblr accounting for 47,480. Twitter received 6,853, Facebook 27, and Instagram 13.

The KCSC last year requested via email to the social-blogging giant to cooperate with authorities to regulate the wide distribution of porn. But the company said it was a US company subject to regulatory oversight by US laws.

Tumblr said it had no physical presence in South Korea and was not subject to local laws. It also said it allows wide-range freedom of expression on its service.

The company also said posts reported by KCSC didn't violate its policy.

The request was sent last year in August but it has been made public only now. It is unclear when Tumblr responded.

Choi said he was very disappointed by the US firm's refusal as the service in Korea has become a "hotbed for illegal prostitution and porn information" in the country.

The MP also heavily criticized the KCSC for only passively reacting to the situation, saying it should cooperate with the foreign ministry to visit the US and ask for the firm's cooperation.