CHICAGO — Governor Pat Quinn rejected a bill Tuesday to expand gambling in Illinois that would have made way for a land-based casino in Chicago, saying the proposal lacked sufficient regulatory oversight.

With his two immediate predecessors in prison, the Chicago Democrat said integrity must be a hallmark of the gambling plan, which also proposed establishing four new riverboat casinos and allowing slot machines at racetracks.

The most glaring omission from the bill ‘‘is the absence of strict ethical standards and comprehensive regulatory oversight. Illinois should never settle for a gaming bill that includes loopholes for mobsters,’’ Quinn said in a statement announcing the veto.

He urged legislators to work with him on its shortcomings, although the bill’s House sponsor said his attempts to meet with Quinn have been rebuffed. Representative Lou Lang, a Skokie Democrat, predicted there would be enough House votes to override Quinn’s veto.