The center-right Union for Popular Movement garnered some 45% of the ballot in this weekend's first-round vote, and is expected to secure about 80% of seats in France's National Assembly after a June 17 runoff, paving the way for Sarkozy's ambitious tax and labor reform plan.
Estimates show that the UMP's current 358-seat majority in the 557-member house may be further increased to 383-470 seats after next Sunday's runoff vote.
The Socialists, whose leader Segolene Royal lost to Sarkozy in last month's presidential elections, could gain between 60 and 170 seats, against 149 in 2002 polls.
The Democratic Movement led by centrist Francois Bayrou, who came in third in the latest presidential elections, is expected to win no more than four seats after polling around 7% in Sunday's legislative ballot.
Several members of Sarkozy's broad-based Cabinet were elected outright on Sunday, including Prime Minister Francois Fillon, Economy Minister Jean-Louis Borloo, Labor and Social Affairs Minister Xavier Bertrand and Defense Minister Herve Morin.