Charlie Riedel, Associated Press
Republican presidential hopeful, former House Speaker Newt Gingrich speaks at a Hy-Vee store in Mt Pleasant, Iowa, Tuesday, Dec. 20, 2011.

OTTUMWA, Iowa — Republican presidential candidate Newt Gingrich is lashing out at Mitt Romney, accusing his chief GOP rival of what he calls a "negative smear campaign" fueled by a political action committee.

Following a campaign appearance Tuesday at a manufacturing plant in Ottumwa, Iowa, Gingrich called on Romney to demand that all ads run on his behalf by political action committees be positive.

Gingrich says that Romney's comments aimed at distancing himself from PAC ads attacking Gingrich are misleading and false.

Gingrich says the PAC that's pouring money into spots attacking him in Iowa in advance of the state caucuses was created by Romney's former staff and funded by his personal wealth.