Rep. Dan Frankel (D., Allegheny) called the present situation "just wrong."
"It is an incredible paradox that we have marriage equality and we don't have nondiscrimination," said Frankel, one of the cosponsors of the bill.
The news conference came on the day that President Obama signed an executive order to ban federal contractors from discriminating against employees based on sexual orientation.
Federal legislation that would bar discrimination is pending in Congress.
Thirty-one states, among them New Jersey, have laws barring discrimination on the basis of sexual orientation. Proponents in Pennsylvania have introduced nondiscrimination bills in every session over the last 10 years.
Even the recent backing of Gov. Corbett has failed to kick-start movement of bipartisan legislation in either the House or Senate, despite claims by supporters that the votes are there.
Rep. Daryl Metcalfe (R., Butler), chairman of the House state government committee, has said he will not move the bill because it "persecutes Christians" who do not want to "help facilitate homosexual activities."
Steve Miskin, spokesman for House Speaker Sam Smith (R., Jefferson), who assigned the bill to Metcalfe's committee, said, "We don't look at bills until they come out of committee."
Several speakers at the news conference alluded to Metcalfe without naming him as the "one person" holding up the legislation.
"It impacts me personally and professionally every day of my life," said Rep. Brian Sims (D., Phila.), the first openly gay elected lawmaker in the legislature. "It is high time this legislation became law. It is an embarrassment to us as Pennsylvanians when we look at our neighbors and see how far they've come on civil rights."
A spokesman for Senate Majority Leader Dominic Pileggi (R., Delaware) was noncommittal about the fate of the bill in that chamber.
"It's an important issue. But at this point we don't have a specific plan in place," said Erik Arneson, Pileggi's spokesman.