SEATTLE (AP) — Seattle's wealthiest would be the only Washington state residents to pay an income tax under legislation approved by the City Council.

The City Council on Monday unanimously voted to impose a 2.25 percent tax on the city's highest earners. Personal income in excess of $250,000 for individuals and in excess of $500,000 for married couples would be taxed.

The measure is certain to face a court challenge from opponents who call the tax proposal illegal, unconstitutional and a waste of taxpayer money. A state law passed in 1984 prohibits a county, city, or city-county from levying a tax on net income.

Supporters say the city's economic growth and prosperity has created significant wealth and opportunity, but has also exacerbated the affordable housing crisis that has put a strain on those in lower income brackets.

They also see the Seattle tax as a step toward building political momentum for the state and its other cities and towns to enact progressive tax systems.