Romney says Obama lifted a provision that required people receiving welfare to work. Independent fact checkers have found the premise of the ad to be false.
Last month, Obama moved to allow states to seek waivers from some welfare rules. To get a waiver, states must show their plans would move at least 20 percent more people to work.
Conservatives say waivers will lead to an end of the work requirement. Romney was among several Republican governors who signed a letter in 2005 asking for more flexibility.
The Obama campaign, noting the work of fact-checking organizations, said Monday the ads are "not true." Campaign spokeswoman Lis Smith said in fact the rule changes strengthen welfare's work requirement, not weaken it. "Just one week after pledging to run a substantive campaign, and whining about the negativity in this race, it's clear Mitt Romney has absolutely no intention of living up to that pledge," she said.
The Romney campaign did not say in which states the ad would run. The campaign says Romney will press thewelfare issue during a town hall in New Hampshire Monday.