The state's teachers' union wants more money for public schools than Governor Andrew Cuomo has proposed, but the governor has spent months warning of a severe budget deficit. So with a new ad campaign, the union is calling for a tax hike on the wealthy.

"New York is home to more billionaires and ultra-millionaires than anywhere else. Income inequality is highest in the nation," the ad says.

While there are a handful of leftover bills from last year that raise revenue through new and restored taxes, there is not yet a bill specificially targeting the ultra-wealthy. But sources tell NY1 there will be one very soon that focuses exclusively on the state's billionaires.

"New York has 112 billionaires with over $525 billion in wealth, and that wealth almost never gets taxed either at the state level or the federal level," said Michael Kink of A Strong Economy for All. "At a time when inequlaity is so extreme, asking billionaires to pay a tiny wealth tax seems like the right thing."

Activists have also joined the campaign using this website which uses the hashtag #makebillionairespay and calls for "budget justice."

Critics of any new taxes say people are fleeing New York State in droves already, and more taxes could make the problem worse.

"People who are leaving our state right now are actually working-class New Yorkers, and if we don't do something to make sure that the quality of life is better here in New York, you are going to see younger and younger generations leaving as well," said state Senator Jessica Ramos of Queens.

With a $6 billion budget gap, Cuomo wants to push more of the burden from ballooning Medicaid costs onto localities, and the teachers' union claims that could leave little money for schools and other priorities.

Both the Democratic state Senate and the governor have made it clear they do not want to raise taxes as part of this year's budget, and it is an election year for all state lawmakers. The Assembly has been more amenable to the idea. Activists hope the wealth tax makes it into the Assembly one-house budget resolution, a statement of the lower house's priorities, expected to pass next month.