Senate Majority Leader Robert C. Byrd, irked by President Carter's failure to mention coal in his State of the Union address, yesterday issued a harsh attack on Carter's energy program.

Noting Carter called the nation's energy problems "the moral equivalent of war" during the last session of Congress, the West Virginia Democrat said, "less than 12 words were in the president's speech about energy and not one word on coal."

"So what has happened?" he asked, pounding his fist on a table. "Has energy suddenly become a stepchild?"

Byrd, who represents one of the nation's largest coal-producing states, also criticized the Carter administration for cutting back on coal research and switching its policy on coal conversion.

"There seems to be a change in energy policy," he told a press conference. "Last year the emphasis was on switching to coal. Now it's on switching to natural gas."

"We have coal mines that are closing in West Virginia and elsewhere; men are being put out of work," Byrd added.

In 1978 Congress passed Carter-backed legislation to encourage industry to convert from oil to coal, the nation's most abundant energy source. It also enacted laws to gradually deregulate the price of natural gas.

Byrd charged that the Carter administration began encouraging industries to switch to natural gas rather than coal when deregulation caused a glut in the natural gas market.

Byrd's comments were the first he has made publicly since he became upset over proposed cuts in coal research and a delay in the construction of two Solvent Refined Coal demonstration plants. The plants, each of which would cost about $700 million, would convert coal to a clean-burning fuel.

In a deal worked out in the Senate, there was an understanding that one of those plants would go to Byrd's home state of West Virginia.

Energy Secretary James Schlesinger requested that funds be put into Carter's 1980 budget to start up the plants. The Office of Budget and Management rejected the requests, demanding that a design competition be held. This, in effect, delayed groundbreaking a year.

Schlesinger appealed the case personally to Carter, but lost.

In his budget released last week, Carter proposed cutting spending on coal research from $681 million in 1979 to $663 million in 1980.

Byrd, speaking at his weekly news conference, also complained that Japan was cutting back on the amount of U.S. coal it imports. This, he said, has increased Japan's trade surplus with the United States to more than $10 billion a year.

"We've talked repeatedly with the Japanese about this," he said. "But they don't seem to get the message."

Byrd said a new Cabinet-level department of international trade should be created to promote U.S. exports around the world. Reiterating a proposal he made earlies last week, Byrd said the department would consolidate U.S. trade efforts now scattered in the State, Agriculture and Commerce departments.