Calcutta HC has held that t is an implied term of the contract between a banker and his customer that the banker will not divulge to third persons, without the consent of the customer, express or implied, either the state of the customer’s account, or any of his transactions with the bank or any information relating to the customer acquired through the keeping of his account, unless the banker is compelled to do so by order of a Court, or the circumstances give rise to a public duty of disclosure or the protection of the banker’s own interests requires
2) in the case of Kattabomman Transport Corporation Ltd. v. State Bank of India AIR 1992 Ker 351, it was held that among the duties of the banker towards the customer is the duty of secrecy. Such duty is a legal one arising out of the contract and is not merely a moral one.
3) you can file complaint against bank before consumer forum and seek compensation for having divulged your bank statement without your consent