"In this way account holders will be put in the condition of choosing whether to keep an account in Intesa Sanpaolo at previous conditions or shift to Isybank," antitrust agency AGCM said in a statement.

The authority had opened a probe earlier this month into the way the country's biggest lender had started shifting thousands of clients.

Isybank, a cloud-based, low-cost mobile bank, is a key plank of Intesa CEO Carlo Messina's long-term strategy to withstand competition from fintech.

The antitrust said that Intesa Sanpaolo had already moved 300,000 customers to Isybank, out of a total of 2.4 million due to be targeted by the move.

It also said it had received 5,000 consumer complaints about the issue.

(Reporting by Giulia Segreti, Editing by Alvise Armellini)