PARIS, Dec 6 (Reuters) - Societe Generale and Credit du Nord have approved a plan to merge their retail banking operations after the boards of both French institutions met separately over the weekend, Les Echos reported on Sunday.

Societe Generale, which owns 80% of Credit du Nord Group, will present detailed plans on Monday for the combination, expected to take 18 to 24 months, the French daily reported.

The bank announced the plans on Sept. 23 as Societe Generale Chief Executive Frederic Oudea stepped up initiatives to overhaul France's third-biggest listed lender - whose shares have since risen 57% from historic lows.

With 10 million clients, the combined entity will generate significant synergies and boost the group's retail banking profitability, Societe Generale has said.

(Reporting by Laurence Frost; Editing by Peter Cooney)