In a conference call with reporters Monday, Brown, a Democrat said he went to the border to "bear witness" on the humanitarian crisis.
"I saw up close the inhumanity and the coldness of President Trump's family separation policy," he said, saying the families he met were "coming to the country to flee violence, flee persecution."
"Tearing them apart, locking them in cages — that is not going to fix our broken immigration policy," he said. "It goes against the values that make this country great."
Portman, meanwhile, said U.S. law has perpetuated the crisis by releasing those who apply for asylum into the community. Many of those he saw who were detained, he said, will be released within days.
"I think people are surprised to learn most folks are simply released into our communities, and aren't held," he said, saying "our laws are actually working to encourage people to make the trip north and get into the country because we don't have an effective asylum policy that enables us to have an expedited way to determine whether someone is in fear of persecution back home."
He said while the children and families he saw in the Donna holding facility were being treated well, he was more concerned about the men he saw in the border facility. "That's where, in my view, the conditions were not something that we want to have in our immigration system," he said, but said the Democrats have contributed to the problem by underfunding Immigrations and Customs Enforcement.
U.S. Senator Rob Portman meets with children at a holding facility near the Mexican border last weekend.