'A work of fiction Stephen King would've been proud of': Republicans are slamming a bombshell study on Trump's tax plan

Republicans are taking on a brutal study of their new tax reform plan, slamming its assumptions and the conclusion that their framework would benefit wealthier Americans.

The study, released by the Urban-Brookings Tax Policy Center, found that the ideas contained in Republicans' nine-page tax reform document would disproportionately favor the wealthiest Americans, while some middle income Americans would see their taxes increase over the next 10 years.

Rep. Kevin Brady, chair of the House Ways and Means committee and one of the "Big Six" tax negotiators, said the TPC report was "misleading, unfounded, and biased."

"Their analysis was a work of fiction that Stephen King would've been proud of," Brady told Fox News Radio on Tuesday.

House Speaker Paul Ryan also brushed off the analysis during an appearance on Fox News.

"It's very predictable coming from this group," Ryan said referring to the TPC. "I think the Wall Street Journal got this right when they said this is an anti-reform, propaganda group. It's anti-tax reform."

Republicans argue that their plan is not yet completed, so any analysis of the plan is premature. The framework does avoid many specifics and contains vague language, which is designed to give the committees writing the legislation some leeway on specific provisions and avoid pressure from lobbyists.

"They're literally making up details, assuming what Congress will do, in order to come up with these kinds of results, to come up with these talking points," Ryan told Fox News.

House Republicans were not the only ones who took issue with the TPC report. Senate Majority Leader Mitch McConnell's office even dedicated a page on the leader's website to attacking the report, citing editorials from various news outlets and stories from years past that attacked TPC.

The other leading tax writer in the Senate, Finance Committee Chair Orrin Hatch, also took issue with the report, noting it contained a disclaimer that it expressed the views of the author.

"Even more unusual, no specific authors were listed on the analysis, probably because no respectable academic or researcher was willing to have their name associated with something so haphazardly cobbled together," Hatch said.

A representative for the Urban Institute did not immediately return a request for comment.