(Beijing) – Flaws in China's political system such as an ineffective system of checks-and-balances must be fixed or officials will continue to become corrupt, a law professor said at a forum at Peking University on January 18.

A major campaign against graft has netted several top officials, but the political system needs further reform for the situation to improve, said Chen Guangzhong, of China University of Political Science and Law in Beijing.

The forum was co-hosted by a legal case research association, a law journal and a media outlet. People invited to attend it voted on the most influential legal cases of last year, and picked the conviction in June of former domestic security boss Zhou Yongkang as the most significant.

Zhou, who became the subject of a corruption probe in 2014, was convicted of bribery, abuse of power and intentional disclosure of state secrets and sentenced to life in prison.

He is the most senior figure to run afoul of Xi Jinping's campaign to clean up government by catching dirty officials, just ahead of the former Communist Party boss of Chongqing, Bo Xilai, who was convicted and jailed for life in 2013 for taking bribes, abusing his power and other offenses.

"We can get rid of one Zhou Yongkang and one Bo Xilai today," Chen said. "But if the system is not fully reformed, it will produce more Zhous and Bos tomorrow.

"We should uphold the party's leadership, but power is controlled by a few top officials. We appear to have a mechanism of checks-and-balances on the surface, but in reality it doesn't work."

Chen said the country's political system should be made more transparent and based on the rule of law. The campaign against corruption should be continued, he said, but officials should be made to disclose their incomes and the public should be given greater access to government information.

Since Xi started his crackdown on corruption shortly after taking the party reins in late 2012, Caixin has counted 46 top military figures; 69 officials with the rank of deputy provincial or ministerial leader; and 115 executives at state-owned enterprises have lost their jobs.

Xi's campaign has shown it is alive and well in 2016. On January 20, Yang Gang, the former party secretary of Urumqi, capital of the far western Xinjiang region, was convicted of taking bribes and sentenced 12 years in prison, the Beijing Third Intermediate People's Court said on Weibo, China's version of Twitter. He and his relatives took 13.79 million yuan worth of bribes from 2008 to 2013, the statement said.

Also, Shen Weichen, the former party chief of Taiyuan, capital of the northern province of Shanxi, stood on trial on January 18, the official Xinhua News Agency reported. He is charged with taking bribes totaling 95.41 million yuan between 1992 and 2014.

The second-most influential case of last year, as voted by the forum's invitees, involved a migrant worker named Chen Chuanjun, who was sentenced to death in 2011 over a robbery case in which one person was killed. A court in the southern city of Guangzhou freed him in August, saying there was not enough evidence to convict him.

(Rewritten by Chen Na)