Czech Prime Minister Petr Necas risked the collapse of his shaky centre-right minority coalition Saturday over a massive corruption scandal in which his top aide was indicted for bribery.

Leftist rival President Milos Zeman said Saturday it was "rather clear" that Necas must step down, while some politicians in the premier's three-party minority government questioned his integrity.

A defiant Necas, however, said Saturday he saw "no reason to resign... early elections are no solution."

His minority coalition in power since July 2010 has so far survived eight confidence votes, and will face another test next week as the Zeman-allied leftist opposition Social Democrats have called a fresh no-confidence motion, likely on Tuesday.

It remains to be seen if the opposition will be able to scramble the 101 votes it needs to topple Necas in the 200-seat lower house of parliament.

In the wake of this week's unprecedented corruption scandal, analysts in Prague have pointed to the possibility of a snap election.

Fresh polls show it would usher the left wing into power. The next regularly scheduled election is due in May 2014.

"The scandal is so serious that Prime Minister Necas can't simply sit it out," Social Democrat party leader Bohuslav Sobotka insisted on Saturday.

But another junior coalition partner on Saturday suggested it would not abandon Necas.

The TOP 09 vice-chairman and finance minister Miroslav Kalousek said the country needed continuity to "help regions and people affected by the floods", which left 12 dead and forced about 19,000 out of their homes a week ago.

The graft scandal rocking Prague erupted when police earlier this week raided the cabinet office, defence ministry, villas and a bank.

Necas's chief of staff Jana Nagyova was on Friday charged with complicity in the "abuse of power and with bribery". She will remain in police custody pending trial.

Seven other people -- including military intelligence heads and former lawmakers -- have also been indicted for corruption among other alleged crimes.

The 48-year-old Nagyova was charged with bribery after allegedly promising three former lawmakers from Necas's party lucrative jobs in state-run companies on condition they quit the parliament.

But police also uncovered instances in which they say Nagyova had abused her power, by asking the head of Czech military intelligence to tail the prime minister's wife Radka, 47, and two other people.

Necas announced this week he was getting divorced from his wife after more than 25 years, amid media speculation that Nagyova was his lover.

Military intelligence chief Milan Kovanda was the only one of the eight charged to avoid custody on Saturday as he confessed to his acts.

Ironically, the premier made a high-profile anti-corruption drive a centrepiece of his coalition.

Necas, a 48-year-old physicist, who on Thursday declared he was confident Nagyova was innocent, on Saturday apologised and said she would be sacked.

"Although I didn't know about these acts, I deeply regret them and apologise to all concerned. I would never accept the abuse of intelligence services for personal and political purposes," Necas said in a statement.

An EU member since 2004, the ex-communist Czech Republic has been plagued by corruption since it emerged as an independent state after its 1993 split with Slovakia.

Corruption watchdog Transparency International in 2012 ranked the Czech Republic as worse than Costa Rica and Rwanda in terms of the prevalence of graft in its "Corruption Perceptions Index".

[Image via Agence France-Presse]