The letter comes a week after the Club for Growth unveiled a set of 30-second ads in Iowa attacking Trump as just another politician who supports liberal policies.
"I am not surprised the dishonest, irrelevant and totally failing Club for Growth has resorted to attacking the definitive front runner, especially after I refused to contribute to their pathetic group," Trump said in a statement. "We will be releasing my current tax proposal, which is a major decrease in taxes, in the next week and will continue to expose the two faced hypocrisy of the Club for Growth and the problems groups like this perpetuate within a broken Washington, D.C."
The cease and desist letter argues that one of the ads is not only "disingenuous, but replete with outright lies, false, defamatory and destructive statements and downright fabrications which you fully know to be untrue." The letter calls out the Club's claim that Trump supports raising taxes, arguing the source for that claim is a gross exaggeration. The Club cited Trump's support in 1999 for a one-time 14.25 percent tax on individual net worth and trusts.
"While a reputable organization would have at least had the decency to disclose its source — and the fact that the source article is more than 15 years old — your pitiful little group conveniently chose to leave that information out in a deliberate attempt to mislead the public into believing that it is reflective of Mr. Trump's current position — when, unquestionably, it is not," the letter said.
Trump and the Club for Growth have been feuding for several weeks. Earlier this month, Trump claimed that the Club had "asked for a ridiculous $1,000,000 contribution."
"I said no way!" Trump said in a tweet at the beginning of the month. The Club for Growth promptly shot back that Trump actually "asked for that mtg & then asked for races he could support. Thought he could buy us off. Worst Kind of Politician."
The Club for Growth did not respond to a request for comment.