An office lease recently signed by Billy Macklowe is fueling speculation that he may be gearing up to break away from his father, Harry.

According to a report in Crain’s New York Business, the younger Macklowe is leasing a small office at Tower 56, located at 125 E. 56th St., suggesting that Billy Macklowe is preparing to conduct business away from Macklowe Properties’ headquarters in the General Motors Building, where the struggling real estate firm occupies 23,000 square feet.

That space in the GM Building costs the Macklowes approximately $2 million a year, an unwelcome expense for a company that has been hemorrhaging money since putting all its chips and personal guarantees into a $7 billion real estate portfolio three years ago, most of which the father-son team has since lost as a result of the recession.

Insiders said Billy had argued against the firm making such a large bet on commercial real estate and later scoured the globe in search of financing to sustain the portfolio.

Billy also assumed the title of chairman and CEO in order to provide comfort to Macklowe Properties’ financiers.

However, the elder Macklowe has continued to try to work deals and angles, most recently, sources said, trying to snare tenants so he could remain part of the development team for the former Drake Hotel site on the northwest corner of Park Avenue and East 56th Street.

That land has since been sold out from under him by lenders.