China denied on Wednesday that Beijing has been manipulating its currency, rejecting an allegation by US Republican presidential candidate Mitt Romney.

"There is no such case of currency manipulation. We will continue to follow the principle of gradual progress and voluntarily reform China's exchange rate regime," Chinese Foreign Ministry spokesman Hong Lei said.

China will continue to gradually allow more flexibility in its currency regime, he added.

During a Tuesday debate Romney described China as a currency manipulator and said he might introduce punitive tariffs on imports of Chinese goods.

"China has been a currency manipulator for years and years and years," he said, proceeding to attack Barack Obama.

"And the president has a regular opportunity to label them as a currency manipulator but refuses to do so. On day one, I will label China a currency manipulator, which will allow me as president to be able to put in place, if necessary, tariffs where I believe that they are taking unfair advantage of our manufacturers."