The city of Dongguan in Guangdong province has never relied on the illegal sex trade for economic growth, Yuan Baocheng, the mayor of the city, said during the annual session of the National People's Congress.

"I have never admitted that Dongguan is the 'sex capital' in China. The city has only one name – that's Dongguan," said Yuan.

Dongguan, in the heart of the Pearl River Delta, was put into the spotlight after the press exposed a rampant illegal sex trade in the city early in February.

"The crackdown on prostitution will last more than three months," said Yuan, adding that local authorities will make the utmost efforts to prevent prostitution in the city.

Yuan said investigation into the illegal sex trade is still in progress.

"We will announce the results in an appropriate time as we are conducting a thorough investigation into cases related to the problem. We need to know how the illegal sex trade begins in the city and who is behind the problem," Yuan said after a group discussion of the annual NPC session on Monday.

Dongguan, one of the world's manufacturing hubs, realized a 9.8 percent year-on-year increase of economic development in 2013, with import and export value reaching $169 billion.