The popular leader of the Madrid region, accused the party's top brass of trying to discredit her. | Javier Lizón

An internal rift broke out in Spain's main opposition People's Party (PP) on Thursday as the popular leader of the Madrid region, seen as a potential candidate for the premiership, accused the party's top brass of trying to discredit her.

Isabel Diaz Ayuso's reelection last May marked a rare convincing win for the conservative PP, which has seen its popularity dwindle over the past decade due to corruption scandals and growing political fragmentation.

Ayuso more than doubled her score of seats from a previous election, propelled to victory by her refusal to close bars and shops during the COVID-19 pandemic, even though the PP trailed far behind the ruling Socialists in national opinion polls.

Now Ayuso says the PP leadership has been trying to collect evidence of corruption against her and her entrepreneur brother over a contract to buy face masks in the early stages of the pandemic.

"The fact is they were preparing a dossier not to seek the truth, but to discredit me personally and politically," she told reporters.

PP Secretary General Teodoro Garcia Egea denied there was any such investigation, accusing Ayuso of "launching unfair, calumnious attacks" against the party's leadership. However, he said the party was studying potential legal action over her remarks.

The rift could further shrink PP's voter base and benefit the far-right Vox, which is the third-largest force in parliament.

"Voters tend to punish internal party divisions. In the context of the PP competing with Vox, this is particularly delicate for the party," said political scientist Pablo Simon from Madrid's Carlos III university.

Ayuso said the face mask contract was fully legal and verified by competent authorities and that she had previously assured PP leader Pablo Casado that she had never given any illegal favours or received kick-backs.

Spain's leftist coalition government, which has been the target of Ayuso's criticism on issues from pandemic management to social spending, said it will investigate the contract.