Federal Reserve Chairman G. William Miller yesterday said the average American buyer is getting dangerously deep in debt, and warned that the trend could have serious consequences, particularly if the United States slides into a recession.

Noting that the ratio of consumer debt to disposable income recently reached a record 20 percent, Miller said, "It cannot continue to go up at the rate it has without danger."

Miller's comments came during a news conference after a closed-door session with members of the Business Council during a two-day meeting here. The Business Council represents the chief executive officers of more than 100 of America's largest corporations.

Several of the natiom's business leaders said they share Miller's alarm over the level to which consumer debts have climbed.

"This is of grave concerns," said Reginald Jones, chairman of General Electric Co. In the past, he said, a debt ratio of 19 percent would almost certainly have indicated as imminent recession. But he blamed inflation for pushing consumer indebtedness past the old milepoints.

"We don't know where the new break point is," Jones said. "We'll find out in the next 12 months."

Meanwhile, Miller, who with his colleagues on the Federal Reserve Board had been criticized by some here for not doing enough to tighten the money supply and thereby restrain inflation, defended by the Fed's efforts.

"There certainly has been application of monetary restraint," he said. Miller pointed to the slower-than-expected growth in the U.S. economy this year and to a predicted crimp in housing starts next year. The Fed Friday raised the rate of interest on loans to member banks to 8.5 percent, the sixth increase this year.

Miller urged the public to be patient, saying that monetary policy has a significant lag time. But he conceded that, despite efforts to raise interest rates and curb spending, individuals still appear to be spending heavily, taking the higher interest rates in stride.

"It's hard to impose restraint," he remarked. "The consumer has accepted these high rates."