The mayor of Zimbabwe's capital, Harare, is facing the sack in the latest wrangle that is threatening to tear apart the main opposition party.
A man saying he was a Citizens Coalition for Change (CCC) official has already got 15 MPs removed after alleging they were not party members.
Sengezo Tshabangu has now written to the government to say Mayor Ian Makone was not part of the CCC.
CCC leader Nelson Chamisa has said Mr Tshabangu was an "impostor".
In a statement on X, formerly known as Twitter, the party has said it is taking legal action against the man "restraining him from falsely representing the CCC".
It also urged "steadfast supporters to remain calm".
A letter by Mr Tshabangu, who described himself as the CCC's "interim secretary general", to the speaker of parliament last month led to the speaker removing 15 MPs. This has triggered by-elections to be held in December.
An attempt by the ousted MPs to get the High Court to overturn the decision failed. But they have taken an appeal to the Supreme Court.
This time, Mr Tshabangu wrote to Local Government Minister Winston Chitando to say that Mr Makone, as well as his deputy Kudzai Kadzombe and seven other city councillors, had "ceased to be members" of the CCC.
He has also written another letter asking the minister to declare 60 local council seats across the country vacant for the same reason.
The minister has not yet responded but could remove the mayor and the other elected officials.
This row could worsen political tensions, which have been running high in the southern African country since August's disputed presidential elections.
Mr Chamisa, 45, lost to incumbent President Emmerson Mnangagwa, 81, in a race that observers said fell short of democratic standards.
The regional grouping, the Southern African Development Community, endorsed the result, despite flagging irregularities in the electoral process.
The 9 December by-elections are unlikely to resolve tensions as Mr Tshabangu has put forward candidates in some of the constituencies under the CCC banner.
Meanwhile, the sacked MPs have filed nomination papers for re-election despite Mr Chamisa saying that the opposition would not participate in what he earlier described as "criminal" by-elections.
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