Francois Fillon savaged Angela Merkel during the televised presidential debate
Emmanuel Macron, a centrist and liberal, is the pollsters’ favourite to win in the French elections in May – coming just ahead of Front National leader Marine Le Pen.
But during a televised presidential debate on Monday night, he was attacked by his rival over a visit he made to Germany this week in which he heaped praise on Chancellor Angela Merkel.
Fillon rejected Emmanuel Macron's comments about Merkel
Mr Fillon roasted his competitor over the hour-long meeting in Berlin, as he launched a brutal offensive on how Germany has tackled the migrant crisis.
And the former prime minister accused Mrs Merkel’s management of refugees as being the cause of huge problems that have faced Europe in recent months.
Fillon has seen his support slide over his fake job scandal
He said: "I completely disagree with Emmanuel Macron who praised the German chancellor when he was in Berlin for (refugee) policies that turned out to be bad policies and which are now criticised by her own allies in Germany.
“The way this crisis was handled has created an enormous problem for Europe.”
Although Mr Fillon belongs to the same conservative party family as Mrs Merkel, he has not shied away from criticising her on a range of issues – slamming sanctions on Moscow as "totally ineffective".
Who will be the next President of France? Mon, March 20, 2017
Candidates for the 2017 French Presidential Election revealed
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The way this [migrant] crisis was handled has created an enormous problem for Europe
The comments come as the top candidates in France's presidential election went head-to-head as polls showed centrist Emmanuel Macron and far-right leader Marine Le Pen pulling away from the pack five weeks before the first round.
Mr Fillon has seen his support slide since being accused of using hundreds of thousands of euros in public money to pay his wife for work she may have not done.
The French presidential candidates went head to head on TV tonight
It is expected he will fail to make it into the second round runoff.
The debate, the first between the five main candidates, may be crucial in helping viewers make up their minds in a bizarre election campaign that has seen major twists and turns.
Opinion polls show almost 40 percent of voters are not sure who to back in the election, which will be held over two rounds on April 23 and May 7.