Q. I am on the board of directors of an Upper West Side condominium. A member of the board is a residential real estate broker who leases and sells apartments in the building — including apartments he’s bought for himself that were substantially below market. As a board member, he has access to privileged resident information, including financials and personal circumstances, giving him an obvious personal advantage in his business deals. Is having this person on the board a breach of our ethical and legal responsibility? What is our obligation?

A: Condominium board members have a legal responsibility to put the interests of the association and all unit owners first. When they use the privileged information they have as board members for their own profit if it’s to the disadvantage of other unit owners, that is a breach of their fiduciary duty.

There is a way that a broker can buy an apartment in a condominium while serving on the board without violating that fiduciary duty: If the member is not influencing how the board treats the purchase application for that unit, and does not vote on whether the board will exercise its right of first refusal when the unit goes up for sale, then there is no impropriety, said Leni Morrison Cummins, chair of the condominiums and cooperatives practice at Cozen O’Connor in New York.

But your situation sounds more egregious. Board members cannot use information they learn in the course of their work for the condominium to influence a buyer or seller, and they cannot use confidential information for their private gain if it harms the condominium or their fellow owners. If this broker is buying units at artificially low prices and then leasing them, he could be dragging down the value of other units.

“At a minimum, this broker should be reminded of his fiduciary duties as a board member, and if he cannot fulfill those duties, he should be given the opportunity to resign,” said Andrew I. Bart, senior counsel with Kagan Lubic Lepper Finkelstein & Gold, LLP.

The board should send a letter to this broker citing the relevant parts of its governing documents. “He should be kept away from discussions of his own transactions and should be reminded of his fiduciary duties not to use confidential information for himself when it comes to his own transactions in the building,” Mr. Bart said. “That’s a red line.”

If your neighbor can’t agree to those demands, he should resign. If he refuses to resign, he should be removed from the board in a process that’s in line with the condo’s bylaws.