The Shadow Open Market Committee, a group of private monetarist economists, praised President Reagan's economic program today but said it would mean less real growth and much larger budget deficits than the administration has forecast.

The committee also predicted, however, that steadily lowering the rate of growth of the money supply, a key part of the administration package, would reduce inflation even more rapidly than the Reagan economists forecast.

Because of the stop-go-stop pattern of money growth in the last year, the committee believes a recession will occur during the middle of this year and that the recovery in 1982 will not be nearly as strong as the administration has forecast.

"We remain confident that [the Reagan] policies will bring the economy closer to its historic real growth path of 2 1/2 percent to 3 1/2 percent -- and bring the inflation rate down to 3 percent by 1985," the committee declared in a statement. The administrationforecast, on the other hand, calls for real output to rise at an average annual rate of 4 1/2 percent from 1982 to 1986, with inflation down to 4.2 percent by 1985.

Allan H. Meltzer of Carnegie-Mellon University, who, with Karl Brunner of the University of Rochester, heads the committee, said the Reagan program was very similar to the sort of economic policy the committee has favored for years. While the 10 members of the group back tax cuts and a smaller government sector, their emphasis is on achieving lower, steady expansion of money.

The committee sharply criticized the Federal Reserve for failing to keep money growth within the bounds of the target range the Fed set for 1980 and expressed concren that the central bank would not be more successful in the future unless it changed its operating procedures.

The Shawdow Committee was formed several years ago in an attempt to bring pressure on the Fed to follow a more monetarist approach in its policies.