WASHINGTON - The head of the Environmental Protection Agency came under sharp attack at a House hearing yesterday, with Democratic lawmakers accusing him of repeatedly caving in to White House pressure on environmental issues such as global warming and a recently enacted health standard for smog.

EPA Administrator Stephen Johnson rejected the characterization and said that although he frequently discusses EPA matters with the White House, the decisions are his.

But Johnson, testifying before the House Oversight and Government Reform Committee for nearly three hours, repeatedly refused to discuss conversations he has had with the White House, and wouldn't provide a number of documents that have been subpoenaed by the committee concerning the smog standard and his refusal to allow California to proceed with rules to cut greenhouse gases.

Rep. Henry Waxman, D-Calif., the committee chairman, said depositions provided by senior EPA staff members suggest that Johnson had been overruled or heavily influenced by the White House on recent EPA decisions on the smog standard, its rejection of a waiver for California on global-warming regulations, and the EPA's ongoing deliberations on whether to regulate carbon dioxide.

"You have essentially become a figurehead," Waxman told Johnson. "In each case, you backed down."

He said in each of the EPA cases "the pattern is the same. The president apparently insisted in his judgment and overrode the unanimous recommendations of EPA scientific and legal experts," said Waxman. "You reversed yourself after having candid conversations with the White House."

Johnson, a 27-year career EPA scientist himself before being elevated to head the agency, repeatedly insisted that he was the final decision-maker on the issues cited by Waxman, although acknowledging frequent discussions with the White House on those and other matters.

Johnson declined repeated requests by Democrats on the panel to provide any details about conversations he had with the White House, refusing at one point to even acknowledge whether he had or had not discussed the smog, California waiver or carbon-dioxide rule-making with the president.

"'I don't think it's appropriate for me to discuss the conversations," said Johnson. *