President Reagan, unabashedly flying the colors of his often criticized economic policies, said yesterday that "Reaganomics" has reduced inflation, cut interest rates in half, started reviving the housing and auto industries, and is now beginning to bring down unemployment.

He asked the American people to stand by him during the coming months of congressional debate on his fiscal 1984 federal budget and to defeat critics who want "to turn away from our economic recovery program and go back to what was being done before."

"In the weeks ahead decisions are going to be made here in Washington that will have a bearing on whether unemployment continues to go down and the economy continues to turn up," Reagan told listeners to his regular Saturday radio broadcast. "You will help determine some of these decisions because public opinion does influence government."

He argued that "all of the good things I've mentioned lower inflation and interest rates, recent upturns in housing starts and auto sales, and the decrease in the unemployment rate announced Friday didn't begin until after our program, Reaganomics, if you will, was put in place. Prior to that everything had been a mess for three years or more."

On Tuesday, Reagan had toured an expanding Missouri auto plant that he cited as evidence of the beginning of economic recovery.

On Friday, appearing buoyant over news that the unemployment rate had fallen from 10.8 percent in December to 10.4 percent in January, he said the economy and the country are "on the move" and predicted that the nation will not again see unemployment as high as 10.8 percent.

Departing from the bipartisan tone of his State of the Union message, Reagan last week stiffened his opposition to rolling back his income tax cuts, funding new job-creation programs or further scaling back his expensive defense buildup. Instead, apparently encouraged by recent rises in several economic indicators, the president began strongly defending his program.

On the radio yesterday, he took dead aim at critics of his economic program. Acknowledging that his economic policies have been labeled "Reaganomics," he said "it sounds like a fad diet or an aerobic exercise," and has been used as a "term for something that is supposed to have failed."

"So if you don't mind," Reagan said, "I'm asking for equal time. . . ."

He argued that his economic program did not begin until Oct. 1, 1981, even though he came to office in January of that year, because the fiscal 1981 budget had been written by the Carter administration. After recounting how inflation was rising, unemployment increasing and the country falling into recession when his economic program was implemented, Reagan asked:

"Now, what has happened in those 16 months of Reaganomics? Well, with the help of the Federal Reserve Board, inflation has dropped to only 3.9 percent for all 1982, the lowest it's been in 10 years. Interest rates are about half what they were. The effect of that is a 40 percent increase in housing starts. Automobile sales are up, as are all retail sales. Factory orders have begun to increase...real wages are up for the first time in three years. And the rate of personal savings is up, meaning more capital for investment.

"And as I've already mentioned, the 'lagging indicator,' as its called, unemployment, just took its first drop....A survey of business establishments shows somewhere around 300,000 more people working."

Reagan said that despite these improvements the government still has record budget deficits, interest rates are "too high," and a third of the nation's industrial capacity is not being used. "We have a long way to go, but that's a start at last," he said, in reference to improvements in the economy since "Reaganomics" has been in place.

In the Democratic response to Reagan's radio speech, Sen. Carl Levin (D-Mich.) said the president has "misunderstood" the meaning of the drop in the jobless rate.

"When looked at closely," Levin said, "virtually all of the improvement in the unemployment numbers results from a reduction in the work force, not an increase in jobs.

"To the president, the new unemployment rate means that his program is working; to me, it means that 11.4 million of our fellow citizens aren't.

"To the president, those figures mean that we are on the mend; to me, they mean that the victims of the continuing recession are still in need of intensive care."