PARIS (Reuters) -The banking arm of French mail operator La Poste is planning to buy banking group BPCE’s stake in French insurer CNP, the companies said on Thursday, and then plans to make an offer to buy the rest of the insurer in a proposal valuing it at 15 billion euros ($17.40 billion). The companies said BPCE would sell the 16% stake to La Banque Postale at 21.90 euros per share of CNP, a 36% premium to its close on Wednesday. La Banque Postale said it would then look to make a formal offer for the rest of CNP, with a view to delist the stock. CNP shares rose 35% on Thursday morning to 21.72 euros. Government-owned La Poste took control of a majority stake in CNP Assurances in 2020, as part of its plans to create a state-controlled bank and insurer focused on France’s rural areas. “The simplification of CNP Assurances’ shareholding structure will allow us to reinforce the efficiency of our bancassurance model, and to accelerate its expansion, in accordance with its multi-partnership and international model,” La Banque Postale Chairman Philippe Heim said. ($1 = 0.8618 euros) Reporting by Sudip Kar-Gupta and Rachel Armstrong; editing by Anil D’Silva and Jason Neely