Alward issued a statement saying Wes McLean, who represents the riding of Victoria-Tobique, was charged last Saturday in Edmundston.
McLean will no longer represent the government on legislative committees, the premier said.
"I take this very seriously and have asked Mr. MacLean to step aside from his legislature duties," Alward added.
The allegations against McLean have not been proven in court. He could not be reached for comment.
Bob Fowlie, director of communications for the Office of Government Members, said: "Wes won't be making any statements at this time."
Alward said it was appropriate to remove McLean from any legislative duties where he represents the government.
"We offer him our support as he goes through the process of repairing his relationship and trust with his community," he said. "Our society has zero tolerance for driving while impaired and our government can expect no less."
McLean won his seat in the September 2010 provincial election.
He was named legislative secretary to the premier and Progressive Conservative deputy house leader in November 2010.
McLean, a resident of Perth-Andover, worked for the New Brunswick government from 2003 to 2004 before serving as legislative assistant to Senator Noel Kinsella.
In 2006, he moved to the Prime Minister’s Office as an adviser on Atlantic Canada. He later worked for the minister of veterans affairs and in the Senate.
Note to readers: This is a corrected story. A previous version incorrectly spelled the surname of Wes McLean.Suggest a correction