PARIS, April 30 (Reuters) - Societe Generale's online bank BoursoBank has "substantial growth" prospects, Chief Executive Slawomir Krupa said on Thursday, adding the lender sees its client base more than doubling over time.

"At 10 million clients, this is not a mature level for this asset," Krupa told analysts on a call. "We believe that down the road, the target... will be 20 to 25 million."

BoursoBank, which competes with Revolut in France, had 8.9 million clients at end-March and contributed 92 million euros to the group's net profit in the first quarter.

(Reporting by Mathieu Rosemain, editing by Inti Landauro)