A security officer stands guard at the Great Hall of the People during the third plenary session of the National People's Congress (NPC) in Beijing, China, March 13, 2016.
Zhu Guangyao said that prospects for economic growth in China warranted a better rating.
"Their assessment for change from stable to negative is absolutely wrong because the IMF just downgraded global economic forecasts 2016 from 3.4% to 3.2% and all advanced economies have been downgraded," he said in an interview with CNBC.
"However, compared with that, the IMF upgraded China's economic forecast from 6.3% to 6.5%… I think the IMF forecast gives us a strong response to ratings agencies," he added
Standard & Poor's last month cut its outlook for the Chinese government's credit rating, maintaining the double-A minus rating but changing the outlook to negative from stable.
Another ratings company, Moody's Investors Service, also lowered its outlook on Chinese debt in the same month.
Guangyao also cited Britain's EU referendum in June, and a possible "Brexit" as a risk to the global economic outlook.
"There's many reason I think some uncertainty will continue increase. … economic development in advanced economies faces a slowdown risk and also geopolitical conflict. And in the