NEW YORK, April 30 (Reuters) - Lawyers who receive documents that were sent by mistake must promptly notify the sender, but they are not necessarily prohibited from using them, the New York City Bar Association said in an ethics opinion released Monday.

The opinion is an effort to address a problem that has grown in the digital age, as electronic communication has become more pervasive.

"We were really trying to clarify an area of ethics and law where there has been a lot of confusion," said Jeremy Feinberg, who chairs the association's professional ethics committee.

Opinion 2012-1 relies on Rule 4.4(b) of the New York Rules of Professional Conduct, which requires lawyers who reasonably know that a document was given to them inadvertently to inform the sender.

The rule applies to all types of communication, including voicemail and emails, regardless of whether the sender is a lawyer, a client or a third party.

A previous opinion, issued in 2003-04 before the Rules of Professional Conduct were adopted, had largely barred lawyers from reviewing or using the misdirected document in question. Since that opinion was more restrictive than Rule 4.4(b), it was formally withdrawn as part of the new opinion, leaving lawyers free to use the information.

The bar association, however, emphasized that lawyers may still determine that it is "right" to refrain from using documents that were inadvertently sent and noted that reading documents that contain privileged information could run afoul of other ethical rules.

"Counsel would do well, however, to remember the New York State Bar Association comment that 'a lawyer who reads or continues to read a document that contains privileged or confidential information may be subject to court-imposed sanctions, including disqualification and evidence-preclusion,'" the opinion states.

(Reporting by Joseph Ax)

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