Illinois’ plan for fixing its $100 billion public pension shortfall is unconstitutional, a union coalition said, suing to restore benefits lawmakers cut to narrow the nation’s worst state retirement-plan deficit, Bloomberg News reported today. The unions described as “theft” legislation that Governor Pat Quinn (D) signed last month to strengthen state pension plans and ultimately save $145 billion with smaller cost of living adjustments and later retirements, according to a statement announcing the suit. The complaint was filed yesterday in state court in Springfield, Ill. Illinois has the worst-funded pension system in the nation and led U.S. states in losing ground every year from 2007 to 2012 in socking away enough assets to pay retired workers. It was the most-populous of five states, including Kentucky, North Dakota, Oregon and Vermont, where pension-funding ratios fell at least 21 percentage points during those years, according to data compiled by Bloomberg.