The official said there were strict restrictions on the use of organs of executed criminals, and such cases were "quite exceptional".
Rights groups say China's transplant business is profit-driven with little regard for medical ethics.
Voluntary donations remain far below demand in China, partly because of cultural biases against organ removal before burial.
Chinese transplant specialists have estimated as much as 99 per cent of transplanted organs come from executed prisoners, according to a report by Amnesty International last year.
The official said organs of executed criminals were used for transplants only when "the criminals have voluntarily expressed the wish to donate their organs … or their families have given consent to such usage".
"There is no difference in the procedures of body or organ donation between deceased ordinary citizens and executed criminals," the official said.
State media reported in November that China planned to tighten its organ transplant rules to prevent patients being abused.
Amnesty International says China executed at least 1,770 people in 2005 - about 80 per cent of the world's total.
China has not revealed the number of executions it carries out.