He was surprised that his city's sex trade industry was as big as it was reported, the mayor of Dongguan told national television on Wednesday.

In response, the city now labeled the "sex capital of China" would take a "surprising measure" in its continuous crackdown on prostitution, announced Yuan Baocheng, mayor of the industrial boomtown in South China's Guangdong Province.

The city government had been incompetent handling prostitution, Yuan admitted on a China Central Television (CCTV) show News 1+1.

"But to be frank, that serious or widespread as the TV report showed, we didn't even expect," he said.

City authorities needed a rethink, he said.

It was the first time since the CCTV exposé was broadcast in February that a top Dongguan government official discussed the issue with the media.

Yuan refused to speak to media in March when he attended the annual National People's Congress in Beijing.

The city government had never turned a blind eye to the illegal trade, Yuan told News 1+1. But certain grass-roots officials had secretly consented to the matter, he said.

Yuan's shock did not convince countless commentators on China's Twitter-like Weibo microblog service, who pointed out that reports about the Dongguan sex industry have widely circulated for years.

Sometimes a social issue is too complex for officials to know fully, but that was no excuse for neglecting their duty, said Yang Weidong, a professor at the Chinese Academy of Governance.

Local governments did turn a blind eye to problems such as the sex trade and counterfeit product factories, he said, as they contribute to local GDP growth.

"Will the crackdown on the sex trade jeopardize the Dongguan economy?" ran a typical headline in Economic Observer in February as media reported widely on the closing down of hotels, night clubs and hair salons in the city.

Tens of thousands of sex workers have lost their jobs in the crackdown, reports said, damaging the city's economy as fewer people visit.

Weibo rumors suggested that prostitution generated 50 billion yuan or 10 percent of Dongguan's 550 billion yuan (S88.7 billion) GDP in 2013.

Yuan did not confirm the statistic, but said the hotels, entertainment, bath and massage venues generated 8.3 billion yuan, or 1.5 percent of the city's total GDP.

"The 8.3 billion yuan is not all from prostitution, drugs and gambling," he said.

Launched a day after the CCTV show, Guangdong Province's three-month crackdown on the sex trade had some "indirect influence" on Dongguan, Yuan said.

Yan Xiaokang, Dongguan vice mayor and head of the city police, was removed from his post for dereliction of duty on February 14, the Xinhua News Agency reported.

Thirty-six Dongguan police officers are under investigation for their involvement in the sex trade.

Dongguan will not stop when the three-month crackdown ends, Yuan pledged.

"The city government will take a surprising measure to continue the crackdown upon prostitution after that," he said.

However "surprising" the measure, Yuan said, he could not guarantee prostitution would disappear forever.