* FGTA-FO backs Prioux in letter to Arnault
* Carrefour working on successor for Plassat
* SocGen's Bernardo Sanchez Incera also seen as candidate
By Dominique Vidalon
PARIS, Feb 21 (Reuters) - Noel Prioux, the head of Carrefour France, got the backing of the main trade union at French retailer Carrefour on Tuesday to succeed chairman and chief executive Georges Plassat.
Some investors have expressed concerns about uncertainty over who will replace Plassat, whose term at Europe's largest retailer ends in May 2018, investment bank Societe Generale said this week.
In a letter to Bernard Arnault, who runs luxury goods group LVMH and whose family holding company is Carrefour's second-largest shareholder, the FGTA-FO union said Prioux was the only candidate able to "maintain a climate of social development so necessary to the group's future".
FO-FGTA secretary general Dejan Terglav also asked Bernard Arnault for a meeting, in the letter addressed to Arnault, a copy of which was seen by Reuters.
The union has no vote at board level, but employees hold 1 percent of the shares in Carrefour, which has not given a deadline for its search for Plassat's successor.
Carrefour, which employs more than 360,000 people worldwide, including more than 100,000 in France, is widely expected to find a candidate by the time of its annual shareholders meeting in the second quarter of this year.
SocGen deputy CEO Bernardo Sanchez Incera has been cited in media reports as another possible successor, along with Carrefour's China boss Thierry Garnier, Carrefour Spain boss Pascal Clouzard, Carrefour's Brazil chief Charles Desmartis and group chief financial officer Pierre-Jean Sivignon.
Staff representatives worry that a new boss could undertake drastic changes, including job cuts, as Carrefour struggles in France, where growth at its hypermarkets slowed in the fourth quarter.
The Moulin family, owner of French department store Galeries Lafayette, is Carrefour's top shareholder with an 11.51 percent stake, followed by Groupe Arnault, with an 8.74 percent stake.
The family of Brazilian retail tycoon Abilio Diniz, also has an 8.05 percent stake in Carrefour.
Since taking over as CEO in 2012, Plassat has focused on price cuts, expanding into convenience stores and renovating stores to boost growth. (Reporting by Dominique Vidalon; Editing by Sudip Kar-Gupta and Alexander Smith)