BEIJING -- Top legislator Zhang Dejiang denounced the serious election fraud in central China's Hunan Province at the ongoing annual parliamentary session here Sunday.

"The case of vote buying that occurred in Hengyang in the province of Hunan was a serious violation of the law and discipline," Zhang told nearly 3,000 lawmakers when delivering a report on the work of the Standing Committee of the National People's Congress (NPC).

"It exerted a baneful influence and gave us a stern warning," he said.

In an election of provincial legislators in Hengyang City of Hunan in late 2012 and early 2013, 56 city lawmakers offered bribes to 518 of their fellow lawmakers and another 68 staff in order to get elected.

The total amount of money involved exceeded 110 million yuan (18.14 million U.S. dollars).

Zhang pledged that the NPC will strengthen the organization and leadership of the election of NPC deputies, act strictly in accordance with the law and prescribed procedures and improve the NPC deputies' way of thinking and conduct.

The NPC must uphold the authority of the system of people's congresses, of socialist democracy, and of the Constitution and laws, Zhang said.