The White House conceded formally yesterday that the economy is in a recession, with inflation likely to continue high and the jobless rate apt to rise substantially. However, officials cautioned against any abrupt change in policy.

In an unusually candid forecast, the administration predicted the economy's "real" output would decline for at least two quarters, and possibly three, with a weak recovery late this year and unemployment rising to 6.9 percent in 1980.

However, a battery of high-ranking economic officials, asserting that inflation still is the nation's No. 1 economic problem, warned against rushing into a general tax cut or job-creation program for fear of worsening inflation.

Urging a steady-as-you-go policy, James T. McIntyre, Carter's budget director, told reporters that "if changes in the economic outlook warrant any . . . modifications in our recommendations, we will consider" them later.

An Daniel H. Brill, assistant secretary of the treasury for economic policy, asserted bluntly that despite the onset of the recession, "we don't see any justification for hitting the panic button" by pushing for a tax cut.

McIntyre also told the briefing that Carter will continue to press for budgetary restraint. He said that while the recession may make it more difficult, "we continue to believe that movement toward a balanced budget remains appropriate."

Meanwhile, sources disclosed that the administration is exploring the possibility of altering its wage-price guidelines to ask businesses to notify the government in advance of major price increases they are planning.

The move, which would affect only a few relatively large corporations, would be designed to help win labor's support for a revival of Carter's once-rejected "real wage insurance" tax credit plan.

Officials are considering the "prenotification" move as one of several options for stiffening the wage-price program for 1979-80. Carter toyed with the idea briefly in 1977, but abandoned it in the face of controversy.

The administration's latest forecast was somewhat less pessimistic and predictions published Wednesday by the Congressional Budget Office, which forecast three full quarters of slightly steeper decline, with higher unemployment.

Nevertheless, the White House figures constituted the gloomiest - and most candid - economic forecast issued by the administration in recent years. Traditionally, presidential forecasters eschew any concession that a recession is coming.

As expected, officials blamed the bulk of the deterioration in the outlook on the recent rise in oil prices, which contributed both to inflation and the recession. However, they also cited soaring food prices and high mortgage costs.

The White House forecast yesterday these elements:

The nation already has entered what officials concede will be a "mild" recession, with "real" output, adjusted for inflation, declining by 0.5 percent in 1979 and edging up a modes 2 percent in 1980.

Inflation will continue at a double-digit pace for most of this year, with consumer prices rising 10.6 percent in 1979, moderating to 8.3 percent in 1980.

Inflation so far this year has surged at a 13.4 percent annual rate.

The unemployment rate will rise to 6.6 percent by late 1979 - from the "full employment" level of 5.6 percent now - ultimately soaring to 6.9 percent or higher by the end of 1980.

Officials said the jobless rate is likely continue rising throughout 1980 even though he recovery already will have been under way for several months because the bounceback will not be vigorous enough to keep job growth rapid.

The picture painted by the White House was for a somewhat milder - and shorter - recession than predicted by CBO. That agency "real" output would dip 1 percent in 1979 and that the decline would continue for nine months.

CBO also predicted the jobless rate would soar to a peak of 7.3 percent by late 1980, and that consumer prices would rise 10.9 percent this year and 8.9 percent in 1980. Both forecasts are in the line with those of private economists.

Despite the extra spending the recession would bring, the White House forecast showed the budget deficit for fiscal 1979 likely to reach only $29.7 billion - $3.5 billion less than projected last March - mainly because of higher revenues.

he deficit for fiscal 1980, which begins Oct. 1, was forecast at $28.7 billion, about the same as projected in March. Higher tax receipts resulting from inflation would more than offset any spending increases from the recession.

As CBO did in its forecast Wednesday, the White House cautioned yesterday that enough uncertainties lingered in the economic outlook for this year and next to raise the possibility that the predictions might be flat wrong.

Lyle Gramley, a member of the Council of Economic Advisers, said the administration now expects the recession to be "relatively short-lived and mild." However, he conceded, "There is a possibility [we] might underestimate" it.

Gramley conceded that yesterday's revised forecast was substantially more pessimistic than the one the administration issued in January, but said the economy "has taken a very abrupt change of direction."

In January, the White House had forecast that the economy would grow by 2.25 percent in 1979 and 3.25 percent in 1980, with consumer prices rising by 7.4 percent in 1979 and 6.3 percent in 1980.