Senate Majority Leader Lisa Brown is working on a possible proposal to create an income tax on the wealthy.

That's the word from her spokesman Jeff Reading, who said Brown "is still working out the details, such as income threshold, percentage, offsets of other taxes, programs the revenue would fund" and language that would pass constitutional muster.

No decision has been made yet, he said. "She's talking informally with members of our caucus."

If they did move ahead, "it's a given that it would have to go to the people," Read said.

There's been a lot of speculation in the past 24 hours that Brown was behind a bill by Sen. Jeanne Kohl-Welles that would create an income tax on the rich.

However, Brown said this morning that Kohl-Welles bill, which would raise around $100 million per biennium, according to a 2007 fiscal analysis, is not "the answer to the structural problem" in the state's budget.

Brown has said in the past she's concerned about what she considers to be an over reliance on the state sales tax.

Here's how she described the problem in a blog post earlier this week:

The Washington Budget & Policy Center argues that we need new revenue to address this budget crisis and many legislators agree with them.

There's been a lot of talk in Olympia recently about a sales tax increase, but we need a revenue proposal that makes things better and fairer for regular families in our state - not worse.

We need to keep in mind that, in Washington, individuals in the lowest 20 percent of the tax bracket pay 17 percent of their annual income in state taxes, and individuals in the top 20 percent of the tax bracket pay less than 3 percent. For a sales tax to be fair, any increase would have to include a full working families tax credit to offset the unfair impact on those who are hardest hit by our tax structure.

I also worry that a sales tax increase would make us even more dependent on an extremely volatile revenue stream. Consider recent evidence: state revenue, more than half of which comes from the sales tax, has taken a nosedive in the current recession. The total downward adjustment of state revenues since the last legislative session is $4.9 billion - $2.3 billion in the past two months alone.

The New York Legislature is considering what I think is a fair and stable way of addressing their revenue challenges.

Should we do something similar in Washington?

Her post links to an article in the New York Times that details a proposal for a temporary increase in the income tax for New York's highest earners.

Conventional wisdom has been that an income tax targeting the wealthy would require a constitutional amendment in this state. And that would require a two-thirds vote in the House and Senate to put on the ballot. Once before voters, it would only need a simple majority vote.

But Reading said the issue isn't that clear cut.

"It's not a foregone conclusion you'd need a two-thirds vote to get out. It's not a guarantee it's a constitutional amendment," he said.

I'll provide more details later on what that means. We've moved our coverage here.