BRUSSELS, Belgium — Once dubbed the Mr. Clean of Czech politics, Prime Minister Petr Necas tendered his resignation Monday, his career cut short by the dramatic arrest of his closest aide, who is caught up in allegations of sex, spies and corruption.

Necas's departure leaves the Czech Republic in political crisis as his center-right Civic Democratic Party seeks to hang on to the prime minister's office while the main center-left opposition demands early elections.

President Milos Zeman, a former social democrat leader, has asked Necas to stay on in a caretaker role pending consultations with party leaders about a replacement.

The scandal that brought about Necas’s fall has further dented the reputation of a country plagued by ongoing charges of high-profile sleaze.

Police from an elite anti-corruption squad on Friday raided the prime minister's office along with other government buildings and private premises. Necas's chief of staff Jana Nagyova was led away by plainclothes officers in ski masks.

She's been charged with bribery and ordering the intelligence services to mount an illegal spying operation. The target was allegedly Necas's wife, which has fueled speculation that the relationship between Necas and Nagyova went beyond the professional.

Necas announced he is divorcing his wife Radka Necasova days before Nagyova’s arrest. He’s denied any romantic connection with his chief of staff.

Two senior intelligence officers and three former Civic Democrat members of parliament were also detained in last week’s raids.

Necas, 48, had been in power for three years. He had pledged to clean up the government and his party when he was elected in 2010.

His predecessor as Civic Democrat leader, Mirek Topolanek was photographed naked in the company of scantily clad young women at the Sardinian villa of Silvio Berlusconi when he was prime minister in 2008.