French President Nicolas Sarkozy on Wednesday ruled out any pact with Marine Le Pen's National Front after its electoral breakthrough but insisted far-right supporters should not be demonised.
As Socialist frontrunner Francois Hollande accused Sarkozy of going too far to "seduce" the far right, European Union president Herman Van Rompuy condemned "winds of populism" which he warned were blowing across Europe.
Hollande won the first round of France's presidential election on Sunday with 28.6 percent of the vote over 27.2 percent for Sarkozy. The two will square off in a final round on May 6 that polls say the Socialist will win.
But the race was shaken up by the 18 percent result of anti-immigration and anti-Europe populist Le Pen, whose score on Sunday was not enough to stay in the race but was the highest ever for a far-right candidate.
Sarkozy, the first sitting French president to lose a first-round vote, has tilted further to the right since Sunday, vowing to "defend the French way of life", drastically reduce immigration and secure France's borders.
"We need to speak to the 18 percent who voted for Marine Le Pen," Sarkozy said in an interview Wednesday with France Info radio.
"But I don't want ministers from the National Front. I've never wanted that. The 18 percent who voted National Front don't belong to me, but it's my duty to address them," he said.
"What Mr Hollande has not understood is that we should speak to everybody. There will be no deal with the National Front, no ministers for them, but I have to take them into account and not feel I have to hold my nose."
His camp has also rounded on a plan in Hollande's platform to give non-EU foreigners the right to vote in municipal elections in 2014, a move Sarkozy's spokeswoman Nathalie Kosciusko-Morizet said would "dismantle citizenship".
Hollande accused Sarkozy of going too far to woo the "divisive" far right.
"Nicolas Sarkozy wants to speak -- and he has the right -- to the voters, as I do, but to flatter, to try to seduce, including leaders of the far right, that goes too far," Hollande told France 2 television.
"It is his responsibility. Everyone campaigns as they want, on their themes, but I think the next president of the republic should be a president who reconciles, who brings people together," Hollande said.
Socialist lawmaker Arnaud Montebourg went further, saying Sarkozy's efforts was giving legitimacy to Le Pen and the far right.
"What he has not understood is that she is stronger than him and she will devour him," Montebourg told Europe 1 radio.
Le Pen is hoping to capitalise on the National Front's strong showing in parliamentary elections in June.
Van Rompuy meanwhile warned that what he sees as the rise of extremist movements and populist nationalism could pose a threat to the free movement of people across the 27-nation European Union.
"Nationalist and extremist movements are on the rise. Many of them blame 'Brussels' for bad news. There can only be one response. Telling the truth," Van Rompuy wrote on Twitter.
"Regrettably, the winds of populism are affecting a key achievement of European integration: the free movement of persons within the EU," he wrote during a visit to Romania.
EU interior ministers will meet Thursday for talks expected to include a French-German proposal to give states more power to restore border checks within the Schengen passport-free travel zone.
The latest poll by OpinionWay released Tuesday showed Hollande beating Sarkozy with 54 percent of the vote in the run-off, a number unchanged from estimates released immediately after the first round.
Le Pen has said she will give her "opinion" on May 1 on who to back, but analysts say it is unlikely she will endorse either candidate.
Polls show most far-right supporters prefer Sarkozy, but up to a quarter -- mainly working-class voters attracted by Le Pen's protectionist trade policies -- could switch to Hollande.
The French left has not won a presidential election in a quarter of a century, but fears over low economic growth, rising joblessness and EU-imposed austerity have given the Socialists a boost.
Many voters also disapprove of Sarkozy's flashy style during his five-year term and have welcomed Hollande's vows to be a "normal president".