By John Irish and Jean-Baptiste Vey


PARIS (Reuters) - Lagging well behind in opinion polls, French Socialist presidential candidate Benoit Hamon accused his main rivals on Thursday of being under the thumb of "big money" as he sought to revive a campaign eclipsed by party in-fighting.


Picked as the ruling Socialist party's nominee in January, Hamon has struggled to make any poll impact ahead the April/May vote after pushing a hard-left program that has divided his party and split the left-wing vote with Communist-backed candidate Jean-Luc Melenchon.


The Socialists, weakened and divided after President Francois Hollande's presidency, are given next to no chance of getting beyond the first round of the election in April.


"This campaign is polluted by money. In the case of some of the candidates, the influence of big money forces can be seen in their programs," Hamon told reporters as he outlined his presidential program.

Hamon appeared to be taking aim directly at scandal-tainted conservative candidate Francois Fillon, and independent centrist and former investment banker Emmanuel Macron, who lie between six to 10 percentage points above him in the polls.

"We're going through a crisis where political officials are less focused on public interest than a raft of interests that they want to satisfy that always find a happy home in their electoral programs," he said.

Fillon, once the frontrunner has seen his campaign derailed by a fake jobs scandal and revelations about his lavish lifestyle. However, he has won plaudits from top business leaders for his proposals to cut 500,000 civil servant jobs, slash the government's bloated costs and make companies more competitive.

Among his top aides is former AXA insurance chief Henri de Castries.

Independent centrist Emmanuel Macron, a former economy minister under Hollande who is now favourite to beat far-right National Front leader Marine Le Pen in May's runoff, has also been questioned by his rivals over his ties with the business community.

"I would like to know if leaders of oil, pharmaceutical companies ... or banks have given a lot, a great deal, an enormous amount to some presidential candidates," Hamon said, requesting that candidates announce who had given them donations.

Presidential candidates can receive a maximum donation of 7,500 euros per individual and there is no legal requirement to make them public.

Hamon, who is currently seen coming fourth in the April 23 first round with between 12-15 percent, has faced dissension within the party. He has pushed a raft of divisive policies including legalizing cannabis, taxing robots, considering cancelling debts between EU states and bringing in a "universal income" for all citizens.

Senior party members have urged him to pull back to the center ground and this week former prime minister Manuel Valls, whom Hamon defeated in the January primaries, said he would not be able to give his backing to Hamon.

"The only program that can be useful over the next five years, useful every day for the French and useful to efficiently fight the National Front, is the one I propose," Hamon said.

(Reporting by John Irish; Editing by Richard Balmforth/Jeremy Gaunt)