On the afternoon of April 16, reporters and lobbyists crammed into a tiny Capitol conference room to watch the House rules committee vote on the long-awaited gas-tax proposal.

Leaders of the GOP-controlled House had been pushing the proposed 3.5-cent-per-gallon increase for months, but this was the first public glimpse of an actual bill. The proposal, which included a host of transportation-related changes, emerged as a 112-page amendment to an innocuous two-page measure on motor-home registration.

Democratic leaders, who opposed a gas-tax hike and had no more clue about what was in the controversial amendment than did reporters, asked how much time they had before the House Republican leadership would call for a vote in the full House to pass the bill.

An hour, they were told.

Yesterday, Common Cause of Pennsylvania filed a lawsuit seeking to void the already-implemented law, arguing that the method of its passage violated Pennsylvania's constitution because the public did not get a sufficient chance to consider it.

``H.B. 67 represents `sneak' legislation, devoid of proper public notice,'' says the lawsuit against Gov. Ridge and members of his cabinet. ``The legislative and executive branch leadership, determined to reduce the legislative process to a meaningless show-piece acted out at the end of the `real' secretive and anti-democratic process, apparently believe that citizen's groups . . . will simply go away. . . . They are wrong.''

Specifically, the suit argues that the bill's passage violated Article III of the state constitution, which reads in part: ``No bill shall be so altered or amended . . . as to change its original purpose.''

Article III also requires that a bill be considered on three days in each house. The motor-home bill met that requirement, but the gas-tax amendment was tacked on just 12 hours before Ridge signed the measure into law, at 1 a.m.

Stephen Drachler, a spokesman for House Majority Leader John Perzel of Philadelphia, expressed disdain for the lawsuit.

``It's unfortunate that Common Cause is once again serving as an obstacle to the public good,'' he said. ``The constitution was followed. There was no deceit.''

Common Cause executive director Barry Kauffman acknowledged yesterday that the method of passing controversial legislation through last-minute amendments was a time-honored Harrisburg tradition.

``But the level to which it has risen is unprecedented,'' he said. Laws to overhaul workers' compensation, deregulate the electricity market, and allow charter schools, as well as an abortive attempt (vetoed by Ridge) to restrict third-party ballot access, were pushed through using that ``fast-track'' method, the lawsuit says.

Controversial legislation often is passed that way, Kauffman said, because ``sometimes the deals are so fragile that they have to run the bill before people have second thoughts.''

Few would dispute that such was the case during the gas-tax debate, when Ridge and the Republicans were dangling road projects to secure what was a razor-thin margin.

``Timing is important,'' Drachler said. ``You don't offer an amendment until you have the votes.''

The suit was filed in both Commonwealth Court and the state Supreme Court.

In 1995, another Common Cause suit led the Supreme Court to declare the procedure used to enact the 1995-96 state budget unconstitutional for similar procedural reasons. But the judges threw out only a portion of the budget. Two subsequent procedural challenges to other laws have failed.