(CNN) - President Barack Obama lashed out Wednesday at those in the U.S. Senate who voted against a compromise proposal to expand background checks on firearms sales, saying those who defeated the legislation "decided it wasn't worth it."
He blamed the defeat of the deal on "the gun lobby and its allies," saying those against the legislation "willfully lied" about its provisions.
"All in in all, this was a pretty shameful day in Washington," he said, as families who lost loved ones in the Newtown school shooting stood around him. Former Rep. Gabrielle Giffords, who was shot in the head in a mass shooting, also stood by his side.
He said "we can do more" to impose stricter gun laws and warned that "if this Congress refuses to listen to the American people ... the real impact is going to have to come from the voters."
He urged people to tell their senators they were disappointed by the vote.
"Those who care deeply about preventing more and more gun violence will have to be as passionate and as organized and as vocal as those who blocked these common sense proposals to keep our kids safe," he said.
"I see this as just Round One," he added.
Mark Barden, the father of a Newtown school massacre victim, said he and others will return home "disappointed but not defeated." He appeared before Obama spoke in the White House Rose Garden.