Republicans are making a mistake by not taking a bipartisan approach and trying to craft tax reform by themselves, Democratic Virginia Sen. Mark Warner told CNBC on Monday.

"If there's one thing we've seen, when either political party tries to do big things only with one side of the aisle, you generally screw up," said Warner, a member of the Senate Finance and Budget committees.

"We saw that perhaps with Democrats when we passed Obamacare [and] Dodd-Frank," he said in a "Squawk Box" interview. "We clearly saw it this year when Republicans tried to do health care."

Warner, a former governor of Virginia and an early investor in technology companies, said he wants to be involved in any tax changes to make sure everyone benefits, not just the rich.

"I spent ... more years in business than I have been in politics. I think I've got something to add to that debate. But so far, there's been no outreach at all," he said. "Nobody calls."

While Warner may not be getting calls on tax reform, not all Democrats are being excluded.

President Donald Trump pushed tax reform last week at an event in North Dakota along with that state's Democratic senator, Heidi Heitkamp, a moderate up for re-election in next year's midterm voting. Trump called Heitkamp, who faces a tough road in her generally Republican state, a "good woman."

Trump last week also reached across the aisle and embraced a Democratic plan for a short-term extension to the debt ceiling packaged with Hurricane Harvey relief.

Warner did acknowledge the president's recent bipartisan efforts. While saying other Democrats and he "were surprised," Warner said he hopes it continues.