The Socialist Party and its Communist and Green allies have won enough seats to gain control of the upper house.

Their victory comes just seven months before the country's presidential election in April.

Right-wing parties have controlled the Senate since the Fifth Republic was founded in 1958.

Early results from the indirect elections showed left-wing candidates took at least 23 seats from the governing conservative party, giving them an absolute majority.

Of the 170 seats up for grabs in the election, Mr Sarkozy's centre-right UMP party had 147 seats out of a total 343 to the Socialist Party's 115 before vote on September 25.

The number of seats in the upper house is being increased to 348 to reflect an increase in population.