"Auckland's mayor needs to work with the Government of the day. I'm willing and able to work with the current Government, and any future Government, to do what's best for the people of Auckland." said Mr Hay.
In February last year, the Green Party suspended Mr Hay for attacking the party's leaders and releasing internal documents. An investigation panel found that he had breached the party's code of conduct and recommended a "cooling down" period of one year.
It said Mr Hay had breached party rules by releasing internal documents which related to the process of choosing candidates. He had also attacked co-leaders Russel Norman and Metiria Turei in press statements.
Labour Party MP Phil Goff is widely expected to announce he is standing for the mayoralty on Sunday at a function at the Royal New Zealand Yacht Squadron.
Other confirmed candidates are Orakei Local Board member Mark Thomas, right-wing candidate Stephen Berry and activist Penny Bright.
Mayor Len Brown announced this month he will not be seeking a third term.
Other possible candidates include former Telecom boss Theresa Gattung, Xero managing director Victoria Crone who has indicated she may stand, and Tex Edwards, founder of 2degrees, who has publised a lengthy prescription for fixing the city, including banishing Ports of Auckland to the Firth of Thames and moving Eden Park to the waterfront.