China's top legislature vowed on Tuesday that election fraud would never be tolerated and promised severe punishments for offenders.

The stance comes on the heels of a notorious case of vote-buying uncovered late last year in Hunan province.

The case was the worst in the history of the National People's Congress, said Fu Ying, spokeswoman for the second session of the 12th NPC, which is set to convene on Wednesday.

It was "severe" and made "a very negative impact", she said.

"We will never allow any behavior that challenges the integrity of the people's congress system. No matter who is involved, where they are, whether they buy votes or have other conduct that disrupts elections, they will be dealt with seriously. There is no exception."

Fu was speaking in response to a question about the electoral fraud in Hengyang, the second-largest city in Hunan province.

The scandal came to light on Dec 28 when the provincial legislature announced that more than 500 lawmakers in the city had been disqualified, dismissed or had resigned.

An investigation revealed that 56 elected provincial legislators had offered 110 million yuan ($18 million) in bribes to 518 municipal lawmakers and another 68 staff members.

The provincial legislature disqualified the 56 on Dec 28, and legislative bodies in Hengyang accepted the resignations of 512 who took bribes during the election of provincial lawmakers between Dec 28, 2012, and Jan 3, 2013.

Hu Guochu, former chairman of the standing committee of the Hengyang People's Congress, is being investigated on suspicion of involvement in the electoral fraud. Fifty-eight suspects have been charged so far.

On Tuesday, Fu called the incident "the most serious electoral breach since the establishment of our people's congress system." Clear electoral and criminal laws exist that ban and punish corruption in elections, she said.

"We'll never tolerate any challenge to the system, and the people concerned have been punished according to the law," Fu said, adding that deputies are representatives of the people and shoulder obligations entrusted to them by the Constitution and laws. "Deputies should have respect for the people and awe of the law," she added.

Contact the writer at zhuzhe@chinadaily.com.cn