Privately owned Leclerc is now France's largest food retailer by market share, having overtaken larger rival Carrefour, thanks to its focus on low prices.

"I confirm that Leclerc is making a start in providing power to consumers ... In a market of 32.4 million consumers, our target is to rapidly become the reference alternative supplier, recruiting three million clients by 2025, or a 10 pct market share," CEO Michel-Edouard Leclerc said on his official blog.

Leclerc said he would provide further details on his plan in September, pledging that the new service Energies E. Leclerc would be "the cheapest in the market".

Leclerc is the second major retailer to enter the power market following Casino, online subsidiary Cdiscount last year started offering retail customers a 15 percent discount to regulated electricity prices.

In the 1980s, Leclerc started selling petrol and its CEO said his firm is now France's second-largest gas station operator after oil group Total.

Despite the arrival of several newcomers in French power retailing, which was opened to competition a decade ago, French state-controlled utility EDF still dominates with a market share of about 84 percent.

Gas and power utility Engie - France's former monopoly gas supplier - is EDF's top challenger and had 3.8 million electricity clients in France at the end of December.

France's main independent power vendor, Direct Energie in April agreed to sell itself to oil major Total which will add 2.6 million new clients to the 1.5 million electricity clients Total already had.

Total is targeting over six million customers in France by 2022.

More than 30 alternative gas and electricity suppliers operate in the French retail market, including Italy's Eni.

(Reporting by Dominique Vidalon; Editing by Geert De Clercq)