PARIS (Reuters) - Centrist Emmanuel Macron saw his position as favorite to win France’s presidential election boosted on Thursday in two polls, with one showing him ahead of far-right leader Marine Le Pen in the first round of the two-stage contest.

A monthly Cevipof survey, considered the most authoritative because it has a far bigger sample size than most polls, put Le Pen well ahead in the April 23 first round, although Macron was seen easily beating her in a May 7 runoff.

However, a Harris Interactive poll showed Macron winning the first round with 26 percent of votes, with Le Pen taking second place on 25 percent, setting him up to trounce her in the run-off with a score of 65 percent.

It was the second poll in a week that put the 39-year-old ahead of Le Pen in the opening round, a signal that the centrist former economy minister may be consolidating his position 45 days from the first stage of the contest.

Le Pen, who leads the anti-European Union, anti-immigration National Front, faced strong criticism of her policies on Thursday from International Monetary Fund chief Christine Lagarde, a former French economy minister.

Without referring to Le Pen by name, Lagarde told Le Parisien newspaper that her flagship policy - pulling France out of the euro - would lead in the short term to “a period of very grave uncertainty, of great imbalance and of impoverishment of France.”

French President Francois Hollande, at a summit in Brussels, said there was concern among his European counterparts about the strength of the National Front. “There is concern because the extreme right is present everywhere in Europe at high levels,” he told a news conference.

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A research note from Credit Suisse bank said, however, that the risk of a Le Pen victory was exaggerated.

Macron's showing in the Harris poll helped ease investor concerns about the prospects of Le Pen winning, with the gap between French and German bond yields narrowing on Thursday morning DE10FR10YT=TWEB.

The race remains difficult to call, though, after a string of surprises, including Socialist incumbent Hollande’s decision not to seek a second term, and surprising wins in primaries for contenders the pollsters had ruled out.

Hollande has asked his ministers to wait until March 24 before stating publicly which candidate they will support. That has led to speculation some senior ministers will throw their weight behind Macron as the best bet to beat Le Pen rather than Socialist candidate Benoit Hamon, who is polling poorly.

Financial scandals have engulfed Le Pen and conservative Francois Fillon, who slumped in the polls after he was accused of using public cash to pay his wife for a ghost job. The latest surveys suggest his support is stabilizing.

After a series of resignations, Fillon’s team announced senior appointments on Thursday to try to shore up his campaign, including former finance minister Francois Baroin in the special role of unifying the increasingly fragmented Republicans party.

Fillon stepped up his attacks on Macron at a rally on Thursday evening, calling him a “golden boy” who was offering disguised socialism.