Chinese authorities are seeking to whitewash the alleged crimes of fallen leader Bo Xilai and protect his political backers by shifting the blame on his wife who will be tried for murder, activists say.

In the biggest political scandal to hit China in decades, Bo's wife Gu Kailai has been charged with homicide over the November 2011 death of British business associate Neil Heywood.

The evidence against her is "irrefutable and substantial", state media said last week, indicating the authorities are intent on settling the case as soon as possible.

But observers said it was much less clear whether wider corruption allegations against Bo would ever be examined in court.

Bo, the son of a revered Communist revolutionary, won national fame with a draconian crackdown on criminal elements and a Maoist-style "red revival" campaign in southwest Chongqing city where he was party boss.

His fall from grace began when his former right-hand man and police chief Wang Lijun fled to a US consulate to seek asylum, after reportedly confronting Bo with information related to Heywood's murder.

Bo's rapid downfall was hugely embarrassing for the Communist Party, and exposed deep divisions at its top level.

Analysts and political activists say the party will be keen to see the back of the scandal, and neutralise the risk it could pose to other senior figures, before a once-in-a-decade leadership transition due in the autumn.

While Bo is being probed for corruption, observers say that Gu's impending trial will now take up the limelight.

"It is the same old thing, they are continuing to cover things up," said former top Communist Party leader Bao Tong, who was purged in 1989 for his role in the Tiananmen democracy protests.

"They will put on a political farce, a fake show, and then when another scandal erupts, they do it all over again," the 79-year-old told AFP.

Gu's trial will be held in eastern Hefei city, far away from Chongqing where Heywood died. Politically sensitive trials in China often take place away from the scene of the alleged crime.

There is speculation that the case could go to court as soon as early August, but no confirmed date has been released.

Heywood is believed to have had commercial dealings with Bo and his wife going back several years.

Activists insist that accounts of Bo's corruption and his wife's alleged crime should be examined in relation to each other, rather than using the publicity over one to whitewash the other.

"To handle Bo Xilai I think you should reveal the whole case, including those who have protected him," Bao said.

"Secondly, they must take Bo Xilai's situation and view it through the relationship with his wife's matter. According to China's law, the assets of a husband and wife are shared, so you can't say that Bo Xilai has no responsibility in the corruption of his wife.

"This is what I hope happens, but so far I have not seen any of this."

Bao said that authorities should probe accounts of the fortune that the couple amassed, and how Gu allegedly became embroiled in what state media called an "economic dispute" with Heywood.

"Right now there is a lot that we don't know because there has been no transparency in the case... and there are a lot of things (the party) does not want people to know about," said prominent rights activist Hu Jia.

"If there is a political struggle inside the party, then they will become even more closed and non-transparent. They won't reach a decision through the judiciary, but it will be a party decision based on political considerations."

Hu said the party's powerful Politics and Law Commission, along with top leaders including President Hu Jintao, will likely decide the fates of Bo and Gu.

The commission is headed by Zhou Yongkang, who is ranked ninth in the party's hierarchy and is reported to be a long-time backer of Bo and his "Chongqing model".

The Chongqing model won popularity for its tough stance on official corruption and organised crime, but has been criticised for operating outside the rule of law and becoming a tool to oust Bo's political opponents.

"Although there are a lot of people raising the problem that the crackdown on organised crime in Chongqing used torture to extract confessions, so far there has not been one case overturned," said rights lawyer Liu Xiaoyan.

Bo will likely be punished by the party, but it is not certain if his case will go to trial, Liu said.