Beijing ( CNN ) -- Chinese authorities have stripped former leader Bo Xilai of his legislative membership , and prosecutors announced they have him under criminal investigation , state-run news agency Xinhua reported Friday . Once a rising political star , Bo 's fall has thrown the ruling Communist Party into its biggest crisis in decades . The People 's Congress of Chongqing , a southwestern metropolis governed by Bo until early this year , has removed his national delegate status , Xinhua said . The moves come ahead of China 's 18th Party Congress , which is convening next month in Beijing . The body will decide who will occupy the top positions in the party hierarchy . Leadership changes once every decade . The Communist Party expelled Bo last month . His leadership positions were taken away in April . Timeline : Bo Xilai 's fall from grace . Bo was once a contender for the Politburo Standing Committee , the team of nine politicians who effectively rule China . But he recently has come under scrutiny , and news reports say he is accused of corruption , abuse of power and improper sexual relationships . Investigators determined that his behavior tarnished the party 's reputation , Xinhua reported , and discovered `` clues to his suspected involvement in other crimes . '' The party investigators have sent their conclusions to judicial authorities . The report said Bo made `` severe mistakes '' related to the killing of a British businessman -- a crime for which Bo 's wife was imprisoned -- and a diplomatic incident involving his former police chief in Chongqing , Xinhua said . It also cited influence peddling , bribery and womanizing as details found in the course of the party 's investigation . Bo is a charismatic and controversial politician . He launched a `` smashing black , singing red '' campaign in the southwestern city of Chongqing that promoted Communist ideology and zealously cracked down on organized crime . His economic programs , which included millions spent on social welfare , made him a popular leader in Chongqing . But analysts say his populist policies and high-profile personal style were seen as a challenge to the more economically liberal and reform-oriented faction that dominates the current party leadership . Bo 's fortunes changed when the dramatic scandal involving him and his inner circle began to seep into the public realm . His wife , Gu Kailai , and family aide Zhang Xiaojun were arrested in early April , suspected of poisoning British businessman Neil Heywood . Heywood died in November in Chongqing , where Bo was the Communist Party chief . His death was originally blamed on excessive alcohol consumption . Bo was soon stripped of his top posts for `` serious breach of discipline . '' In August , his wife received a suspended death sentence after a seven-hour trial . Days later , four senior Chongqing police officers were also sentenced to jail for covering up the murder . In an e-mail dated early October obtained by CNN , Bo Guagua , the son of Bo Xilai and Gu Kailai who lives in the United States , reiterated his belief in his parents ' innocence and asked his maternal grandmother to find a lawyer for his father . `` Although I miss my parents every minute , I feel they are with me in my heart , '' the younger Bo wrote . `` Wherever they are , they will hold their heads high and be the fearless and transparent people that they are . '' `` I do n't know politics -- but since the state wants to have the rule of law , I believe its decision on my father also must go through a fair legal process , '' he continued . `` Now I am helpless and you are the person closest to me -- I would like to entrust you with the task of finding an appropriate lawyer to defend my father . '' A friend of the Bo family , who declined to be named due to the sensitivity of the story , told CNN the family has hired two Beijing-based lawyers to represent the former politician in impending criminal proceedings . The lawyers have not been allowed to visit Bo but they do n't expect a trial to take place for another few months , the friend added . Wang Lijun , the former police chief of Chongqing , set off the Bo story on February 6 , when he fled to the U.S. Consulate in Chengdu and told American diplomats that Gu was a suspected accomplice in a murder case . After his request for asylum was turned down , Wang left the consulate and was taken away by Chinese officials . But his accusations rocked the world 's most populous nation . Wang was sentenced to 15 years in prison last month for defection , cover-up , bribe taking and abuse of power . The party expelled Bo after an investigation of the killing and Wang 's visit to the consulate , a trip made `` without permission , '' Xinhua said . The investigators said Bo `` bore major responsibility '' in the Wang incident and the killing , Xinhua reported . Son defends disgraced Chinese politician Bo Xilai .
Report : Bo Chung is under criminal investigation , he said . Bo is a former political prisoner who was earlier stripped of legislative membership . Bo 's party investigated him for influence peddling , bribery and womanizing .