In a speech Wednesday night at the Democratic convention, Sister Simone Campbell, star of the "nuns on the bus" tour that has traveled the nation criticizing Rep. Paul Ryan's (R-WI) budget, knocked the Romney-Ryan approach to economics saying it was "immoral" because it disregards the needs of the most vulnerable members of society.

In the speech, Campbell spoke of the Christian ideal of helping the needy. Especially at a time of economic hardship, Campbell said, it was the government's responsibility to exemplify that ideal and to help the neediest citizens.

"Paul Ryan claims his budget reflects the principles of our shared Catholic faith," she said. "But the United States Conference of Catholic Bishops stated that the Ryan budget failed a basic moral test, because it would harm families living in poverty."

Alluding to the Bible, Campbell said, "I am my sister's keeper. I am my brother's keeper."  And she drew rapt applause while relating the stories of several people she'd met on her bus tour, all of whom she said exemplified the case for a collective effort to aid the needy. In one example, Campbell told the story of two ten-year-old boys in Ohio who were found to be secretly caring for their ailing mother. Once the community learned of the situation, they stepped in to help. It's that kind of community effort, Campbell said, the government should help promote.

"Clearly, we all share responsibility for the Matts and Marks in our nation," she said, referring to the two ten-year-olds.

While President Obama would care for the most needy, Campbell said Ryan and Romney's approach to the budget showed that they did not share the same sense of generosity and understanding.

"Together, we understand that an immoral budget that hurts already struggling families does not reflect our nation's values. We are better than that," she said.

Watch the whole speech below: