For weeks now, it has been clear that a deepening economic recession is making hash out of the Reagan adminstration's economic game plan. Not only was the prospect of a balanced budget in fiscal 1984 so ludicrous that it had to be abandoned by the president, but the size of the deficits ahead began to assume frightening proportions.

Three sets of numbers tell a grim story. In July, the Office of Management and Budget delivered these budget deficit estimates, which assumed there would be no serious recession:

Fiscal 1982 -- $42.5 billion

Fiscal 1983 -- $52.7 billion

Fiscal 1984 -- $44.2 billion

As unemployment climbed and factory output fell, OMB revised its data so that, by November, it had changed its internal projections of the deficits as follows:

Fiscal 1982 -- $96.7 billion

Fiscal 1983 -- $126.5 billion

Fiscal 1984 -- $145.7 billion

And this week, the OMB, basing its estimate on an assessment by the Council of Economic Advisers, upped the deficit this way:

Fiscal 1982 -- $109.1 billion

Fiscal 1983 -- $152.3 billion

Fiscal 1984 -- $162.0 billion

Thus, in the space of just a few months, the administration was forced to admit that the deficit for the current fiscal year had doubled. And the three-year budget outlook had exploded from a cumulative deficit of $139.4 billion to $423.4 billion, mostly because of recession and to a lesser degree because high interest rates had swelled the cost of financing the national debt.

Each percentage point increase in the unemployment rate automatically boosts the deficit by about $25 billion a year because revenues fall off and unemployment payments soar. But the Reagan administration is standing pat. Beyond abandoning the ipossible balanced budget goal for fiscal 1984, the president is clinging to what is surely an untenable do-nothing position.

On Dec. 3, Economic Council Chairman Murray Weidenbaum, while assuring that the huge budget deficits are not regarded with "indifference," had this to say:

". . . the president's program plus the built-in stabilizing elements in the federal budget are ample assurance that the appropriate policies for dealing with the near-term situation, as well as the long run, are already in place, 'baked into the cake,' if you wish. That they also happen to be the critical elements in achieving our long- term objectives is not simply coincidence, but a reflection of their fundamental soundness."

Baloney. The notion that an all-wise administration has established an all-purpose program, good for all eventualities, short-term as well as long-term, just won't wash. It is greeted with dismay in the business world, which believes that if the administration hasn't lost its senses it will respond with a "Phase II" of Reaganomics in January. Phase II would recognize that no president can send an official budget forecast to Congress incorporating anything like the new budget deficits for fiscal 1983 and 1984.

They can't be brushed aside, as Weidenbaum and his colleague, William Niskanen, tried to do this week by suggesting--inaccurately--that deficit control was never a top priority in the Reagan campaign, and that besides, deficits aren't too damaging to the economy.

As an influential outside adviser to the administration told me: "They are going to have to come to grips with the deficits. They can't do anything about the current fiscal year, but they must make deeper cuts in the entitlement programs, or reduce the big increase in military spending, or raise taxes --or some combination of these things."

Of course, this is what David Stockman was saying in the now-famous Atlantic Monthly article. But it is the reverse of what the supply- side "loyalists," led by Treasury Secretary Donald T. Regan, have been telling the president.

The real question is how long Reagan and Regan will cling to a no-tax-increase position. The well-publicized fears of local and state Republican officials, such as Gov. Richard A. Snelling of Vermont, that social program cuts have already gone too far show clearly that basic repairs must come through tax increases and Pentagon budget reductions.

No one is arguing that taxes ought to be raised in recession year 1982: in this respect, everybody seems to be a Keynesian, including --unwittingly--the supply-siders, who are anxious to accelerate the mid-year 1982 stage of the Kemp-Roth tax cut, which is nothing more than an old-style, Keynesian tax reduction.

But if the economy does get over recession, and is expanding in fiscal 1983 and beyond (as Murray Weidenbaum is forecasting), Reaganomics, unaltered, could touch off the kind of Draconian Federal Reserve policy that will make a 20 percent prime rate look cheap.