With New York in a budget crisis the likes of which it hasn’t seen in decades, a City Council leader says now is the time to open the books, eliminate wasteful spending and save some serious cash for schools and other causes.

The city should end billions of dollars in tax exemptions and other funding for developers and cancel huge contracts with big firms doing vague jobs, Councilman Ben Kallos (D-Manhattan), the chair of the Council’s Committee on Contracts, wrote Mayor de Blasio on Monday night.

He identified up to $15 billion in possible cuts and savings, saying nearly $1 billion of that could go to schools, social services and other causes that are facing steep cuts in the wretched economic climate.