"The recently announced waiver policy was originally requested by the Republican governors of Utah and Nevada to achieve more flexibility in designing programs more likely to work in this challenging environment," he wrote in a statement released late Tuesday from his foundation.  "The administration has taken important steps to ensure that the work requirement is retained and that waivers will be granted only if a state can demonstrate that more people will be moved into work under its new approach.  The welfare time limits, another important feature of the 1996 act, will not be waived."

He called Romney's assault -- which includes an ad -- "especially disappointing because, as governor of Massachusetts, he requested changes in the welfare reform laws that could have eliminated time limits altogether. We need a bipartisan consensus to continue to help people move from welfare to work even during these hard times, not more misleading campaign ads."

The Romney camp responded with a statement charging that Obama was a "vocal opponent of the innovative, bipartisan welfare reforms that President Clinton and a Republican Congress passed in 1996."

And spokesman Ryan Williams doubled down on the assertion -- which earned a Pants on Fire from independent fact checkers Politifact: "His administration has now undermined the central premise of those reforms by gutting the welfare-to-work requirement. Unlike President Obama, Mitt Romney has a record of fighting to strengthen work requirements. As president, he will ensure that nearly sixteen years of progress aren’t erased with one stroke of a pen."

The Obama campaign has put up a web video that concludes "Romney, flexible on welfare .. and the truth."