The Czech Republic's opposition Social Democrats won control of the Senate for the first time on Saturday, giving them the power to stop sending more Czech troops to Afghanistan and to delay unpopular spending cuts.
The results, announced by the Czech Statistical Office, suggested that voters punished the new center-right government for its proposed austerity measures in the race for 27 seats in the 81-seat Senate. The top two finishers from last week's first round had a two-day runoff.
The left-wing Social Democrats won 12 Senate seats, which, with the 29 seats they had that were not up for re-election, gave them a majority of 41 seats.
"It's a very important moment for the Social Democrats," the party's interim leader Bohuslav Sobotka said. "(We have) become a decisive force in the Senate."
Prime Minister Petr Necas' conservative Civic Democratic Party won just eight seats, for a total of 25.
Parliament's lower house dominates the legislative process, but the Senate plays an important role in electing the president and in passing constitutional amendments. The next presidential election is in 2013.
Having a Senate majority will allow the Social Democrats to scrap a government plan to increase the number of troops in Afghanistan by 200 next year, up to 720 total.
Although the loss is a blow to Necas' three-party governing coalition, the Social Democrats will not be able to completely block his planned austerity measures, including a 10 percent cut in state employees' salaries.
The government is trying to reduce the Czech Republic's budget deficit from 5.3 percent of gross domestic product this year to 4.6 percent next year, a plan that has pleased rating agencies but not opposition lawmakers or labor groups.
But the opposition can now delay approval of the austerity measures until next year.
Necas claimed the loss will not harm the government's austerity plans, including an overhaul of the country's pension system, but acknowledged that it will make it harder to pass laws.
"The result will delay and complicate the legislative process, that's reality," he said. "We're ready to negotiate."