Republican presidential candidate Rick Perry isn't backing off his claim that Social Security is unconstitutional. In fact, he is now calling the program a "monstrous lie."

In his book "Fed Up!", the Texas governor wrote that Social Security was put in place "at the expense of respect for the Constitution and limited government."

Last week, Perry Communications Director Ray Sullivan tried to walk back those claims by saying the book was "not meant to reflect the governor's current views on how to fix" Social Security.

But when confronted by ThinkProgress' Scott Keyes Saturday in Des Moines, Iowa, Perry said his views were still in line with the book.

"I haven't backed off anything in my book," Perry grumbled. "Read the book again, get it right."

Earlier that day at the The Vine Coffeehouse, Perry told a voter that Social Security was "ponzi scheme for these young people."

"The idea that they're working and paying into Social Security today, that the current program is going to be there for them, is a lie," he said. "It is a monstrous lie on this generation, and we can't do that to them."

Watch this video from ThinkProgress, uploaded Aug. 27, 2011.