French President Francois Hollande's Socialists and allies came out on top in first-round parliamentary elections, poised to secure the majority needed to push through tax-and-spend reforms.
The election also saw a surge in support for Marine Le Pen's far-right National Front, which wants to ditch the euro and battle against what she calls the "Islamisation" of France.
The Socialists, Greens and allies won around 46 percent of the vote, ahead of the 34 percent for ex-president Nicolas Sarkozy's right-wing UMP party and its allies, the final results released by the interior ministry showed.
Pollsters TNS Sofres, Ipos and OpinonWay agreed that the Socialists and close allies might win between 283-329 seats in the 577-seat National Assembly or potentially as many as 329 and could hold power in the parliament without relying of the votes of the Greens or the anti-capitalist Left Front.
Hollande defeated Sarkozy in last month's presidential election and wants voters to give him a strong mandate to enact reforms as France battles Europe's crippling debt crisis, rising joblessness and a stagnant economy.
If next week's second round confirms Sunday's results, it will boost his status in Europe as champion of the movement away from German-led fixation on austerity towards growth, which he favours as the solution to the economic crisis.
The daily Les Echos on Monday summed up the media mood on the elections, talking of a "measured support for the president."
A month after Hollande's victory at the polls, "there was no red wave, and there was an unprecedented failure to mobilise voters," it added.
Nationwide turnout was put at 57 percent, a record low for a first round of legislative elections.
However Hollande's Prime Minister Jean-Marc Ayrault, re-elected in the first round voting in the Loire-Atlantique region, hailed the results and urged voters to return to the polls in numbers for the second round to hand a "large, solid and coherent majority" for the Socialist party and its allies.
"Change is going to be around for a while," he said, echoing the Socialists' presidential election slogan.
The National Front won 13.6 percent of the votes, far above the 4.0 percent it achieved in the last parliamentary election in 2007.
But under France's first-past-the-post system, that would at best give it only three parliamentary seats and possibly none at all.
The Communist-backed Left Front, headed by firebrand anti-capitalist Jean-Luc Melenchon, won 6.9 percent of the votes.
The night marked a personal defeat for Melenchon who took Le Pen head-on in a bitter battle in a rundown former mining constituency near the northern city of Lille.
"It's normal to be disappointed but we must not be defeated," Melenchon said as he bowed out, while Le Pen claimed her victory meant her party was now France's third political power.
"Given the abstention rate and a profoundly anti-democratic electoral system that has for 25 years deprived millions of voters of MPs, we confirm our position tonight as France's third political force," Le Pen said.
Although the party has not won a seat in parliament since 1986, Le Pen is seeking to build on her strong showing in the presidential vote and cement her party's place in national politics.
Melenchon won 11 percent of votes in the April-May presidential vote that was won by Hollande, while Le Pen won almost 18 percent of votes.
Centrist leader Francois Bayrou meanwhile appeared set to lose his seat in the southwest after his left and right-wing rivals beat him in the first round.
Hollande has pledged to hire an extra 60,000 new teachers and to hit top earners with a 50-percent tax rate on some of their income.
The Socialists took control of the upper house of parliament, the Senate, last year.
Ayrault's interim government has taken a series of popular steps in the wake of Hollande's presidential victory in the May 6 run-off.
He has cut ministers' salaries by 30 percent, vowed to reduce executive pay at state-owned companies and lowered the retirement age from 62 to 60 for some workers.
But the UMP has hit back with warnings that the Socialists are preparing huge tax hikes to pay for what the right says is a fiscally irresponsible spending programme for Europe's second-biggest economy.
UMP leader Jean-Francois Cope said the Socialists were readying "the biggest-ever tightening of the screws on the middle class".
The economic backdrop is bleak for whoever wins the parliamentary vote: unemployment is at 10 percent, growth has stalled and the eurozone crisis has lurched back into the foreground.
More than 6,500 candidates competed in Sunday's vote, which takes place over two rounds under a constituency-based simple majority system.
If no candidate wins more than 50 percent in the first round, any contender who scores more than 12.5 percent of the vote can stay in the race for the second round.