WASHINGTON — The Treasury Department said Thursday that a communications firm with close ties to President Obama talked to the administration about allowing tax breaks for its corporate clients on more than $1 trillion in offshore revenues.

Hilary Rosen, a partner at the firm, SKDKnickerbocker, who is also a prominent Obama supporter, arranged a phone call last year with Jake Siewert, then a senior adviser to Treasury Secretary Timothy F. Geithner, to determine whether the administration might reverse its position on the offshore tax issue, according to a department spokeswoman.

Mr. Siewert said the administration would not, the spokeswoman said.

The firm has insisted that it never spoke with senior Treasury Department officials about the offshore tax issue and that it does not lobby policy makers on issues affecting its corporate clients. Jill Zuckman, a partner at SKDK, said Thursday that Ms. Rosen “did not remember having that conversation” with Mr. Siewert.

One of the firm’s top executives is Anita Dunn, a confidante of Mr. Obama who served as his White House communications director and is now a top campaign adviser. The firm’s growing list of corporate clients, including businesses that have sought to change the administration’s policies on issues including food advertising, energy and taxes, has attracted scrutiny in part because of Ms. Dunn’s high profile.