BEIJING (Reuters) - An expose of corruption at the top level of China’s centuries-old petition system has confirmed public fears of flaws in the setup and sparked calls for greater reform.

Since ancient times, many of China’s disenfranchised, as a last resort, have aired their grievances to the top leadership in Beijing using written letters and in-person visits.

The State Bureau for Letters and Calls in Beijing receives petitions and visits by individuals and channels their complaints and grievances to the relevant government entities.

But for years, top officials in Beijing, including the former vice chairman of the bureau, Xu Jie, took bribes to make cases disappear, according to an article published on Sunday by Prosecutorial View.

Xu had amassed gifts and cash worth 5.5 million yuan ($796,900) and was jailed for 13 years in 2015, the official magazine of the Shanghai government prosecutors said.

Xu and a crew of underlings had helped local bureaux from across China fiddle the details of cases so they never appeared in the records, helping to avoid embarrassment for the provincial officials, the magazine said.

The disclosure also threw light on the teams of provincial public security and letters bureau agents who live in Beijing, in theory to help petitioners from their locality.

In practice, these teams often illegally detain people in off-grid locations known as “black jails” and forcibly make them leave the city so as to stop them causing trouble.

Such people “openly use funds to bribe the National Letters and Calls Bureau officials so as to block the ear of the central government,” said a commentary published on the official Guangming Net on Monday.

“The National Letters and Calls Bureau case reflects structural problems in operations of the national administration,” it said.

“If these structural problems are not resolved at the system level, then the revealed issues will not be thoroughly settled.”

Six million petitions are submitted each year across the country, and in 2014, more than 250,000 personal visits were made to Beijing, according to bureau statistics.

Online commentators also honed in on the system’s inbuilt faults, saying central government directives for regional governments to keep the number of petitions low could be encouraging corruption.

“Keeping the number of letters and visits down is an important measure for assessing local government officials,” said popular post about the article by a user called Wuyue Sanren on Weibo, China’s version of Twitter.

“As (petitioning) is itself not judicial... it’s not at all surprising that there is space for rent-seeking by those with power.”