By Adrian Croft
PARIS (Reuters) - French presidential candidate Francois Fillon, an outsider to win after involvement in a financial scandal, said on Monday he would order a parliamentary inquiry into allegations President Francois Hollande interfered in the justice system, if elected.
Once the frontrunner, the conservative former prime minister's poll ratings have slumped since allegations surfaced that he paid his wife, a son and a daughter hundreds of thousands of euros of public money for minimal work.
Fillon, 63, who is being investigated by magistrates over the jobs allegations and over a gift of expensive suits, insisted on his innocence.
"If I had the slightest doubt about my guilt I wouldn't be a candidate in the presidential election," he told BFM TV.
He said he was the victim of "manipulation", but drew back from previous allegations that Hollande, a Socialist president who is not standing for a second term, had personally led a smear campaign against him. He said he could not prove this.
He said however that prosecutors should open an inquiry into allegations made in a book by two journalists from satirical weekly Le Canard Enchaine that Hollande had judicial wiretaps that interested him sent to his office.
"Prosecutors should take up this case. If they don't do so and if I am elected president, there will be a parliamentary commission of inquiry," Fillon said.
Hollande's office has rejected Fillon's accusations and denied interference in the justice system.
Two polls on Monday showed far-right leader Marine Le Pen and centrist Emmanuel Macron neck-and-neck in the race, with each predicted to receive about 25 percent of the vote in the April 23 first round.
Macron had a half-point lead over Le Pen in an IFOP-Fiducial poll, while an Opinionway poll gave Le Pen a one-point lead over Macron. Both polls had Fillon lagging well behind in third place.
Only the top two candidates go through to the May 7 run-off, where polls predict Macron would easily beat Le Pen, who wants to take France out of the euro and hold a referendum on EU membership.
All 11 candidates will take part in a televised debate lasting more than three hours on Tuesday evening, one of the main opportunities for many of them to reach a wide audience.
Investors are concerned the wave of frustration with political elites behind Britain's vote to leave the European Union and the election of Donald Trump in the United States could sweep Le Pen into power in France.
Former Prime Minister Manuel Valls said last week he believed Le Pen's potential vote was being seriously under-rated.
Macron told Le Monde in an interview on Monday that Fillon and Socialist candidate Benoit Hamon were wrong to focus their attacks on him, when Le Pen was the real threat.
"Those who say Marine Le Pen can't win the second round are the same as those who said Trump could never win. We don't know what can happen if she is far ahead in the first round," he said.
(Additional reporting by Michel Rose; Editing by)