Democrats have been left in the dark on the details of the Republican tax deal in what has been a "very secretive" process, Rep. Raul Grijalva, D-Ariz., told CNBC on Thursday.
"Procedurally, this process both at the House and in the Senate has been very rapid, very secretive, minimal if none public input at public hearings," Grijalva said in an interview with "Power Lunch."
He said the differences between the two bills were supposed to be reconciled during a conference between members of the House and Senate on Wednesday, which he attended.
"Unfortunately the ruling by the majority at that conference … was that that wasn't going to occur," he said.
"There was no ability to make motions, to change, to strike, to amend" parts of the legislation.
The agreement between House and Senate Republicans came before the conference, leading Democrats to slam the event. Sen. Bernie Sanders, I-Vt., called the meeting a "farce."
The Republican deal features a 21 percent corporate tax rate, starting in 2018, and a top individual rate of 37 percent, CNBC and other outlets reported. It would also allow a mortgage interest deduction on loans up to $750,000.
Not all Republicans are on board with the plan, yet. Sen. Marco Rubio, R-Fla., opposes the current legislation unless the GOP expands the proposed child tax credit. Sen. Mike Lee, R-Utah, is currently undecided and also wants to expand the credit.
Meanwhile, Sen. Bob Corker, R-Tenn., opposed the Senate version and hasn't committed to backing a joint bill yet.
If both Corker and Rubio vote against the tax proposal, one more GOP senator opposing it would sink the bill.
Republicans are hoping to have a final bill passed next week to send to President Donald Trump to sign into law.
— CNBC's Jacob Pramuk contributed to this report.