Kereke lost his parliamentary seat last week after the party said he could not represent Zanu-PF in Parliament because of a rape case three years ago that has still not been heard by the courts.
Kereke, a former adviser to the central bank governor, has been involved in a spat with his former boss, Gono, whom he has accused of stealing millions of United States dollars from the bank, which Gono has denied.
Sources in Zanu-PF's politburo told the Mail & Guardian that Kereke could not be trusted because, in the past, he had threatened to expose alleged corrupt activities by Gono.
The fear, they said, is that he may end up implicating other high-ranking officials in the party, who believed he must be shown the door.
Kereke has previously threatened to submit evidence of the looting of diamonds from Chiadzwa to Parliament and, after winning a parliamentary seat in the July elections, sources say he posed a risk of pressing for a parliamentary probe that would embarrass senior officials.
Kereke's political problems are mounting as prosecutors have allegedly come under intense pressure in recent weeks to prosecute him for the alleged rape of an 11-year-old relative at his Harare home in Vainona.
Sources who were at Zanu-PF's politburo meeting this week said Kereke had been all but ditched by the faction — led by Justice Minister Emmerson Mnangagwa — who supported Kereke.
President Robert Mugabe allegedly told the meeting that Kereke was unacceptable to the party, despite winning a parliamentary seat for it.
A politburo source says, in the tense meeting, Vice-President Joice Mujuru's faction raised the matter of Kereke's outstanding rape case and it was swiftly concluded that he must go to court, which was endorsed by Mugabe. No one in the Mnangagwa faction came to his defence.
Gono has long been a Mugabe favourite, which the media claim is because he has acted as Mugabe's personal banker.
Before the July 31 polls, members of Mujuru's faction pushed to have Elias Musakwa stand for the party in Bikita West.
As a result, the Zanu-PF politburo blocked Kereke from standing as its candidate, citing his pending case.
Disowned by Zanu-PF
Musakwa is also a former Reserve Bank employee. However, Kereke connived with the party's provincial leadership in Masvingo, where he comes from, to sign his candidature papers on behalf of the party, which were accepted by the Nomination Court.
The provincial members are now being subjected to a party internal disciplinary hearing.
Traditional chiefs and war veterans in the Bikita constituency, among whom Kereke is extremely popular, rallied behind him and Zanu-PF ended up fielding two candidates in the constituency.
Despite the split and the odds heavily stacked against him by the Zanu-PF machinery, Kereke won the seat.
But his triumph has been short-lived as the speaker of the National Assembly, Jacob Mudenda, expelled him from Parliament on Thursday last week after Zanu-PF disowned him.
"I hereby inform this honourable House of the provisions of the Electoral Act that a vacancy exists in the membership of Parliament in the National Assembly — the seat of Bikita West constituency," Mudenda told a plenary session of Parliament.
Mudenda said the seat had become vacant because of a declaration made to him on September 30 by the Zanu-PF secretary for administration that "Dr Munyaradzi Kereke, who was a member of that party at the time of his election, has ceased to be a member and no longer represents the interests of that party in Parliament".
Zanu-PF cited section 129 of the Constitution, which says an MP's seat becomes vacant when a political party writes to Parliament to say that the holder of the seat is no longer one of its members.
Zimbabwe does not permit floorcrossing. It was reported on Thursday that Kereke has applied to the Constitutional Court to challenge his ejection from Parliament but he could not be reached for comment.
The lawyer representing the parents of Kereke's alleged rape victim, who cannot be named as she is a minor, has also stepped up the pressure, filing an application in the High Court demanding that he be prosecuted.
The lawyer, Charles Warara, claims a long time has passed since the police handed a docket to the attorney general's office that allegedly claims Kereke has a case to answer.
'Innocent until proven guilty'
In an interview, attorney general Johannes Tomana said his office's position is that Kereke is innocent until proven guilty.
He added that his office must uphold the Constitution and would not act like political parties, which can choose to say people are guilty before they are convicted.
"Everyone must be treated as innocent until proven guilty, so even Kereke is innocent until proven guilty. We are guided by facts in the docket and by the law," Tomana said.
"Other parties may treat people [as] guilty based on half-truths but it is a crime to push us to prosecute or to encourage us under the Constitution.
"But, on that [Kereke's] case, you can ask the director of public prosecutions where we are."
The director of public prosecutions was not available for comment but Warara said this week he had lodged papers in the High Court to compel the attorney general to prosecute the matter.
Warara said he was waiting for the matter to be set down and for the prosecutors to state their position formally.
"The police say they have evidence. We have lodged an application to compel prosecution. If they don't proceed, we will go for private prosecution," said Warara.
Kereke and Gono
Munyaradzi Kereke rose to prominence as an adviser to central bank governor Gideon Gono at the height of the country's hyperinflation in 2008.
They were at the helm of the bank when it implemented controversial fiscal policies such as continually printing money and raiding the foreign-currency accounts of private companies to prop up a government facing economic collapse.
The policies were highly unpopular with the public and fuelled inflation that reached 213-million percent in 2008. Kereke later fell out with Gono and left the bank.
He alleged that Gono had stolen $100 000 from him and that Gono had forced Kereke to write Gono's PhD dissertation. He also said he had evidence that Gono had stolen millions from the bank.
In 2010, the rape case allegedly involving Kereke emerged. He has denied guilt.
He is reportedly close to army generals who benefited from his tenure at the Reserve Bank at the height of hyperinflation.
In 2011, the Standard's reporter and editor were arrested for reporting that a new health insurance firm, Green Card Medical Society, owned by Kereke, was on the brink of collapse.
The Zimbabwe Union of Journalists then ditched Kereke as a sponsor, saying that, by pushing for arrests instead of approaching the Voluntary Media Council, he showed he did not stand for press freedom.