With Mr Sarkozy and Ms Royal facing off in a final poll on May 6th, who Mr Bayrou's seven million voters turn to now is a major deciding factor in the race to succeed Jacques Chirac.
But at a highly-anticipated press conference he simply said: "I will not give any guidance about how to vote," admitting that he himself was unsure about who would receive his ballot paper.
Mr Bayrou, who also used today's media briefing to unveil a new democratic political party, said UMP leader Mr Sarkozy would "worsen problems of democracy and the social fabric of France" if elected president.
And although he said Ms Royal was more of a democrat than her rival, Mr Bayrou claimed her presidency would be undermined by an "unbalancing of the economy and increases in the country's deficit".
Urging French voters to "rebuild our democracy", he said France was a country "that worries, which suffers, which is torn".
"France has three problems: we are a country with an ailing democracy; we are a country with a torn social fabric; we are a country with no growth," Mr Bayrou continued.
Interior minister Mr Sarkozy received 31.2 per cent of the vote earlier this month, compared to Ms Royal's 25.9 pre cent.
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