The Carter administration's simmering interagency battle over air pollution rules for coal-burning power plants burst into the open yesterday.

Barbara Blum, assistant administrator of the Environmental Protection Agency and a longtime Atlanta supporter of President Carter, attacked Energy Secretary James R. Schlesinger's proposal to relax clean air laws in order to encourage coal burning.

In a speech before the Conservation Foundation, Blum said "I must respond" to a June 4 memo from Schlesinger to Carter that was leaked to the press last week. "About the last thing that's needed to solve the energy crisis is another skirmish outside the main arena. However, for me to stay silent poses a greater risk," she added.

Blum said the policy of both the president and Congress "is to burn not only more coal but burn it more cleanly. In my judgment this is a wise course, placing priority on both our nation's energy wellbeing and public health.

"To retreat from the commitment [to clean air] would be dead wrong - dead wrong for government, for industry and, most of all, for the American people."

The EPA has approved permits for 74 new coal-fired power plants, which will increase the nation's use of coal by 25 percent by the early 1980s. By the 1990s the administration wants to more than double coal use, in order to slow escalating oil imports.

Schlesinger would like to make it cheaper for utilities to burn coal by eliminating the Clean Air Act's requirement that they build scrubbers to remove sulfur, which causes respiratory disease, water pollution and crop poisoning.

Instead of scrubbers, Schlesinger says, utilities should use intermittent controls, allowing sulfur emissions to vary with the wind conditions. Sen. Edmund S. Muskie (D-Maine) calls intermittent controls "the rhythm method of pollution control and about as effective."

Blum said the EPA is not delaying conversions of existing power plants from oil to coal, as critics have contended. The conversion of a Somerset, Mass., power plant recently approved by the EPA, will cut New England's oil dependence by 17 percent, she said.

Asserting that Schlesinger's goal of 2.1 billion tons of coal production by the year 2000 is "likely to be met," Blum contended that "the crunch we're in today involves a shortage of liquid fuels - gasoline for cars, fuel oil for heating homes . . . [and] coal will not fill this gap . . ."