Madrid president Isabel Diaz Ayuso has accused leader Pablo Casado of spying on her family.
The President of the Madrid region is under investigation after accusing the leader of her own party of plotting to destroy her.
Isabel Díaz Ayuso has slammed Popular Party (PP) leader Pablo Casado for allegedly waging a smear campaign.
The party's deputy leader Teodoro García Egea confirmed that they had opened disciplinary proceedings against the Madrid president.
Spain's main opposition party has endured an internal struggle over leadership following last year's regional elections.
Díaz Ayuso gained great popularity during the COVID-19 pandemic for her stance on health restrictions and the reopening of the city's hospitality sector.
She has often been hailed as the future PP leader but has clashed with current party chief Casado.
On Wednesday, Díaz Ayuso accused her party leader of spying on her to uncover alleged corruption within the Madrid region presidency.
There are claims that the Madrid president signed a contract for facemasks, due to her brother's personal relationship with a company.
Díaz Ayuso directly accused Casado -- and the party -- of trying to discredit her "personally and politically" and linking her to corruption "without evidence".
"I could never have imagined that the national leadership of my party would act so cruelly and unfairly against me," she said on Wednesday, insisting that "there is nothing illegal" about the contract.
Her remarks have sparked anger among other leading figures in the Popular Party, and García Egea has said that her comments were "almost criminal".
"This party will not tolerate any attack on its honour... and that the leadership that has given it everything is attacked in such a cruel and unjust way," García Egea said.
Díaz Ayuso now faces internal disciplinary action and could be suspended from the party for four to six years or even expelled.
The Popular Party fell short of an absolute majority in Sunday's early elections in the region of Castilla y León and could be forced to form a coalition with the far-right Vox party.
Spain is not due to hold its next national election until 2024.