British Chancellor of the Exchequer Denis Healey said here yesterday that the most important task facing the economic summit in London next month is to assure that the world does not "slip into recession" in 1978.

Healey is here for a meeting of the International Monetary Fund's policy making Interim Committee later in the week.

In an address to the national Press Club, Healey said business and financial communities all over the world need assurance that "the president pace of recovery will be continued next year."

Concern has been expressed, the British treasury official said, that expansion "might peter out," leading to higher unemployment and recession.

Healey indicated two basic ways in which the summit scheduled for May 7 and 8, might provide hope for sustained recovery. Fisrt, the more affluent countries such as the United States, West Germany and Japan could use the summit forum to promise that they "can achieve the [economic] growth targets they have set for themselves."

And second, he hopes that the summit will in various ways speed the process of aid suffering balance-of-payments deficits.

One such plan backed by the United Kingdom and other European countries is a common fund to stabilize earnings that poor countrieds derive from sale of commodities.

Another is a substantial expansion of IMF resorces - one of the primary items on the Interim Committee agenda this agenda this week. Yesterday the U.S. government lent its weight to creation of a special IMF lending pool which could be as much as $16 billion, equal shares to be contributed by the wealthy industrial nations and the oil cartel countries.

Healey told the Press Club audience that, without some such lending pool "bridging the gap" until more money flows normally into the IMF through enlarged quotas, the impact of world-wide payments deficits would be deflationary.

By inference, Healey also warned that disregarding less affluent countries would accelerate Communist Party influence in Europe. He pointed out that Communists had gained increasing power "where the existing system doesn't meet the need.

"If we want to retain the free enterprise system, we will have to influence (changes in) the international monetary system."

In a related development yesterday, the IMF granted Zaire credits equivalents to about $85 million to help stabilize that African nation's ailing economy.Zaire agreed to an austerity program that will help cut a high rate of inflation.

Healey, who had been encouraging an extra measure of expansion among the leading countries as an aid to other nations' recovery, said he was not disturbed by President Carter's withdrawal of $11 billion in stimulus through the $50 income tax rebate.

The American administration, Healey said, believes it will still achieve a 6 per cent growth rate from the end of 1976 to the end of 1977, "and many figures suggest that this may well be so." However, at the end of last week, the administration shaves this economic growth projection to 5.7 per cent.

Healey was relatively optimistic about securing renewal of a "social contract" with British labor unions that would limit earnings increases to about 10 per cent in the coming year, compared with 9 per cent this year: "It will be difficult, but I expect to get it."

Since the "painful" decisions Britain had to make last December in order to obtain a $3.9 billion loan from the IMF. "Our financial situation has been transformed." Healey said, citing a 16-cent rise in the pound, to $1.71, and "record reserves that can beat off any attack against the pound."

If a new social contract is achieved, he predicted that Britain's current 16 per cent inflation rate will fall to 12 per cent at the end of 1977, to "single-digit" by the second quarter of 1978, and to 7 per cent in the summer.