Walter McClure, a spokesman for the commission, said that under law, he could not comment on anything that might relate to an investigative matter.

The inquiry by the ethics panel, which has the authority to bring administrative actions and seek fines, is separate from more than a half-dozen federal and state criminal investigations that in recent months have examined various aspects of the mayor’s political fund-raising. One of those, being conducted by federal prosecutors in Manhattan and the Federal Bureau of Investigation, has also focused in some measure on the Campaign for One New York, according to people briefed on the matter.

Critics have raised questions about the relationship between the nonprofit and Mr. de Blasio, who had an active role in fund-raising for the group.

The questions include whether the group was simply working as an arm of his campaign and whether giving money to it may have been a way for those with business before the city — or those seeking such business — to curry favor with him without being subject to campaign-finance limits.

The nature of that relationship seemed even murkier after the Albany judge’s ruling, when Mr. de Blasio’s response seemed to tacitly acknowledge that there was little separation between the nonprofit and him and his administration. When asked why the nonprofit had refused to comply with the subpoena, Mr. de Blasio said, “We disagree with judge’s final judgment, and so we’re exploring appellate options at this point.”

The Campaign for One New York is what the Internal Revenue Service characterizes as a social welfare nonprofit, which means that it was supposed to work primarily to promote the common good and welfare of an entire community. Such nonprofits, which include groups like the Sierra Club and the National Right to Life Committee, are allowed to participate in politics — as long as politics does not become their primary focus.

In its incorporation papers and documents filed with the I.R.S., the group said that its purpose was to “advocate for One New York and New York City by informing the public and policy makers about legislative and public policy options.”