PARIS: Emmanuel Macron's political party is to name a new leader on Saturday as the French president faces the first rebellious grumblings in the movement he founded in April last year.

Six months after coming to power in a sensational upset for French politics, Macron's Republic on the Move (LREM) will hold its party congress in the western city of Lyon, where Christophe Castaner is expected to be selected as leader.

Macron's handpicked favourite, Castaner is an ultra-loyal smooth-talking government spokesman who joined the 39-year-old head of state's team early in his run for presidency.

He is standing unopposed in a vote set to be dominated by national party bigwigs -- which has upset some of the grassroots members of what Macron called a "citizens' movement".

After widespread grumbling in private, a small group of 100 followers went public this week with an open resignation letter that claimed the party had no internal democracy and was consumed by political games.

The anonymous rebels said in the letter published by France Info radio station on Tuesday that LREM was guilty of "contempt and arrogance".

The complaints are one of a number of challenges faced by Macron, who needs the party as a support base as he battles opponents on many fronts, including angry trade unionists opposed to his agenda.

Even senior figures admit that, since tasting glory over the summer with a membership that swelled to more than 350,000, the party has stagnated.

LREM will be vital for Macron at the local and regional level in France, where future elections for mayors and councils offer him the chance to push his pro-business agenda to "transform" France.

Launched simply as En Marche (On the Move) in April 2016, it was a hugely effective electoral force with its thousands of volunteers who knocked on doors, flocked to rallies and distributed leaflets.-AFP