House Republicans kicked off the legislative effort to pass comprehensive tax reform legislation Thursday with a highly anticipated hearing in the Ways and Means Committee.

As the Republicans used the meeting to highlight their goal of a permanent reform of the entire tax code that does not add to the government's deficit, Vice President Mike Pence promised a historic tax cut in a speech at the U.S. Chamber of Commerce.

The Trump administration and congressional Republicans have been aiming to unite on one plan for tax reform, and leaders met Wednesday afternoon at the Capitol to plot the way forward.

Thursday's hearing was the first step in the legislative process. Led by Committee Chairman Kevin Brady, R-Texas, the Republicans once again staked out their demand that the legislation be a permanent tax reform, rather than a temporary tax cut as the White House has suggested is a possibility.

"You've made all a very compelling argument for bold tax reform, permanent tax reform, and doing it now," Brady told the witnesses, a panel of business leaders including executives at AT&T and S&P Global.

In one exchange with the witnesses, tax subcommittee Chairman Peter Roskam of Illinois sought to get the witnesses to emphasize the importance of permanently changing the tax code for making business decisions.

"Knowing that and having that allows us to make consistent, significant material capital investments," said John Stephens, the chief financial officer for AT&T.

The debate over permanence versus settling for temporary tax cuts, which might be easier to move through Congress, is one that will play out among Republicans.

Thursday's hearing, however, gave Democrats a chance to weigh in on the state of the tax code, despite the likelihood that their votes will not be sought in the final bill.

Several raised concern that the House Republican outline would cut taxes for high earners without benefiting middle-class families.

Rep. John Lewis, the Georgian famous for his leadership in the civil rights movement, faulted the witnesses at Thursday's hearing for lacking diversity.

"Look at the panel. Just look," he said, pausing for effect. "All white men. Where are the women? Where are the minorities? Where are the little people?"