A group of well-known conservative economists said yesterday that there will be no sustained economic recovery unless President Reagan agrees to budget compromises that will reduce soaring deficits in the future.

The group, the Shadow Open Market Committee, is comprised mostly of monetarist economists who normally pay far more attention to monetary policy and to actions of the Federal Reserve than to fiscal policy. While they also had some harsh words for the Fed, the emphasis was on the budget.

If the prospective budget deficits are not reduced, the results may lead to "a decline in real income and standards of living and an economic crisis," the committee warned in a statement. "Or the economy may continue to limp along the path characterized by low productivity growth, rising real transfer payments and a rising size of government."

The latter possibility, which committee co-chairman Allan H. Meltzer of Carnegie-Mellon University termed "stagflation," or an inflationary and sluggish economy, is the best that can be hoped for if the deficits are not slashed.

Specifically, the committee urged limiting cost-of-living adjustments in federal entitlement programs such as Social Security and cutting back Reagan's proposed large increases in defense spending. It said any tax increases "should be limited to federal excises and/or a surcharge on imported oil" of about $5 a barrel.

The committee rejected any easing of monetary policy beyond what the Federal Reserve already has announced for this year. Its monetary target, expressed in terms of the monetary base--a measure that includes only currency in circulation and reserves held by financial institutions--would be equal to about a 5 1/2 percent growth in the money supply, the upper limit of the Fed's target range for 1982.

The huge prospective budget deficits and the erratic growth of the money supply are causing increasing uncertainty in the financial markets and are helping to keep interest rates at unusually high levels compared with the rate of inflation, the committee said. As it has in the past, the group recommended a number of technical changes in Federal Reserve procedures to enable it to come closer to its monetary growth targets.

Reducing the budget deficits for the years after 1982 and keeping money growth consistently within the Fed's target range will "work toward lower interest rates and sustained noninflationary growth of output," the statement said.

H. Erich Heinemann of Morgan-Stanley & Co. said a recovery will begin some time within the next three or four months. But Heinemann said it would not be a strong recovery and that the economy probably will turn down again in 1983 unless major policy shifts are made. The other two forecasts, by Robert Genetski of Chicago's Harris Bank and Burton Zwick of Prudential Insurance Co., did not show a decline in 1983 but called for growth far slower than the 4 percent to 5 percent rates predicted by the administration.