France's far right accused the big two parties Sunday of muzzling democracy by trying to exclude its candidate from the presidential election.

Despite strong public support, National Front chief Marine Le Pen said last week she was still 150 signatures short of the 500 from elected local officials, such as mayors, that she required in order to stand.

National Front Vice-President Louis Alliot suggested establishment parties were indirectly encouraging elected officials not to give her the backing she needed.

(There are) political calculations aimed at muzzling democracy and preventing all opposition to the establishment, he said.

Le Pen is running third in opinion polls, with 15 to 20 percent of voter intentions ahead of the April 22 first round but, like her father Jean-Marie in 2002, hopes to knock out one of the frontrunners to reach the two candidate runoff on May 6.

At one point in January she was a couple of points behind incumbent Nicolas Sarkozy but has since slipped back.

Alliot said suggestions from both the frontrunning Socialists and the conservative ruling UMP party that there was no problem with the current system were outrageous.

It seems the establishment is trying to impose the idea that the absence of Marine Le Pen would not be a problem, he said in a statement.

Prospective candidates have until March 16 to secure enough signatures and Le Pen has taken her case to France's highest court to challenge the 1976 rule, arguing that many officials would rather choose anonymously and as a result are boycotting the process.

The Constitutional Council is set make its decision before February 22.

According to a newspaper poll published Sunday, Sarkozy would benefit most if the former lawyer was unable to stand.

The survey for Journal du Dimanche showed the president would pick up 8.5 points, while his Socialist challenger Francois Hollande would win 3.5 points more, leaving them level on 33 percent after the first round.

Her opponents say Le Pen is bluffing and her suggestion she may not get sufficient official backing is a ploy to promote her status as an outsider and to remain in the public eye.

Le Pen, who replaced her father as party chief last year, has tried to broaden the National Front's appeal beyond its traditional anti-immigrant base to a younger generation with a more anti-euro and protectionist stance.

She says a failure to secure 500 endorsements, like her father in 1981, would represent the end of French democracy, given that a fifth of voters would be effectively denied a vote.

Defense Minister Gerard Longuet said Sunday it would be a backward step if Le Pen failed to make it through. She represents a political trend and this movement should be able to express its views, he said.

But we have to ask ourselves why not even 1 percent of (about 36,000) mayors are not signing up for her. Maybe it's because she says some absurd things.

French presidential rolling poll: http://r.reuters.com/was36s

(Reporting By John Irish; Editing by Ben Harding)