China's ruling Communist Party expelled an allegedly corrupt former railways minister on Monday, more than a year after his dismissal. The lengthy process underscores the party's challenges as it grapples with how to handle the tricky case of an even higher-profile official accused of grave violations of discipline.

The party's discipline body said the former railways minister, Liu Zhijun, had taken massive bribes and abused his authority to help a private businessman make huge illegal profits, according to the website of the official party newspaper People's Daily.

It also accused him of fostering major corruption throughout the country's railway system and having "degenerate morals," a term that often refers to sexual liaisons and the keeping of mistresses.

Liu's case will now be handed over to prosecutors, who will formally charge him. Getting kicked out of the Communist Party virtually guarantees a conviction.

Liu was removed as minister in February 2011, and the lengthy course his case has taken speaks to the unique problems the party faces in dealing with Bo Xilai, a member of the party's Politburo once considered a candidate for its all-powerful Standing Committee when a new generation of leaders is named this fall.

Bo was removed as party boss of the southwestern mega-city of Chongqing and suspended from the Politburo on March 15, days after publicly defending himself against rumors of self-enrichment and abuse of power. He is under investigation for unspecified violations, while his wife and an orderly at their home are accused of homicide in the death of a British businessman.

The party was widely seen as hoping to tidy up the scandal well ahead of the party congress expected around October, but it is unclear how much progress has been made.

"They have to come up with an announcement, the earlier the better so as to allow a cooling-off period and limit the impact on the party congress," said Joseph Cheng, a China politics expert at the City University of Hong Kong.

Taking down high-ranking officials is always a risky undertaking, and the abuse or scandal involved must be truly egregious to warrant the attempt.

Liu had been railways minister for eight years, far exceeding the usual term for a minister. He accumulated vast wealth and power while in office, especially during a headlong rush to extend the bullet train network nationwide.

High-speed rail was a national prestige project aimed at showing off China's technological prowess and rising wealth while linking its far-flung regions.

But the bullet train network came under heated criticism following a crash last July that killed 40 people in the eastern city of Wenzhou. In the wake of the accident, the government was forced to lower the speed of trains amid criticism that the system was dangerously fast and too expensive.

Allegations of kickbacks, bribes, illegal contracts and other malfeasance had circulated around Liu for years, but the ministry's outsize influence and his own personal authority seemed to shield him from formal accusations.

The government has since crimped the Railways Ministry's powers, cutting back on investment as funding grew tight and putting railways-related court cases in most regions under the jurisdiction of civilian courts, rather than the railway court system.

Bidding on railway projects was also recently brought in line with procedures for other government public works.

State media said that was intended to ensure fairness and transparency and prevent officials from meddling in project bidding or engaging in influence peddling or collusion.

Monday's reports gave no word on the fate of another senior official, Zhang Shuguang, an engineer in charge of research and development of the country's high-speed railways, who was removed alongside Liu for unnamed disciplinary violations.