A sharpening decline in world trade and the recessive impact of austerity programs are reinforcing a period of economic stagnation in Western Europe that bankers and economists believe may persist through the end of the decade.

The simultaneous need among some countries in the 10-member European Community to rectify trade imbalances is hindering the kind of export growth that nurtured the continent's postwar prosperity and is badly needed now to break out of the doldrums of recession.

"We've run out of easy solutions," explained an International Monetary Fund official who closely monitors the European economic scene. "It now appears to be a matter of simply letting the deflationary cycle complete its course."

Herbert Giersch, head of West Germany's Kiel Institute for World Economy, said he is pessimistic about chances for a solid recovery before 1990 because "the corrective process" of keeping wages below productivity gains may take that long until "our economy gets uncramped again and it pays to create new jobs."

Since the European Community was formed in 1957, the continent's economies have grown so intertwined that countries now depend greatly on each other's boom or bust phases to balance their trade.

The current recession, however, has lodged every major European nation in a downward trend that has diminished world trade and exacerbated unemployment.

The IMF reports that world trade volume declined $30 billion last year and may fall another $80 billion this year.

Last week, the European Community revealed figures that showed unemployment among member states rose in September to a new postwar high of 9.8 percent.

International economists fear that many countries may be tempted to resort now to policies that would further encumber trade, such as protectionist measures or competitive devaluations.

In the past year, Sweden, Finland and Belgium have devalued their currencies, while France has done so twice.

In each case, governments were eager to stimulate exports by discounting prices of their goods in foreign markets and discouraging imports by making them more expensive.

Nonetheless, France has discovered that a 27 percent decline in the franc's value since last year has actually worsened its trade balance because more costly imports outweighed a slight rise in exports. External Trade Minister Michel Rocard recently declared that he anticipated a $14 billion trade deficit this year.

France's troubles also portend more problems for West Germany, its biggest trading partner.

West German exports account for 29 percent of the country's gross national product, a proportion that makes it acutely vulnerable to economic difficulties among its neighbors.

The Bonn government has been banking on an economic recovery in the United States next year and a gradual upturn in other European countries to fulfill its own hopes for a resurgence of growth.

"It is by no means certain that this will happen," said Olaf Sievert, an economist who headed an independent body of five "wise men" assigned to study prospects for West Germany's economy.

"It is possible that even more restrictive measures in France, or in the Netherlands or in Great Britain could change the scenario so much that . . . this will affect German exports, which would do much worse," said Sievert.

Unless recovery in the United States and Europe is unexpectedly robust and opens up new export possibilities, West Germany may not be able to live up to its past role as the "locomotive" that pulled other European countries out of previous slumps.

"We have to assume that trade will not be up to levels of the past 30 years," said Herbert Wolf, a senior economist at Commerzbank, West Germany's third-largest bank. "There is no major country in the world today without major problems."

IMF officials claim that throughout Europe, industries have suffered such a tight squeeze on profits due to high taxes and wage costs that key investments needed to bolster productivity have been neglected since the mid-1970s.

Governments have also grown more wary of providing huge subsidies to keep companies afloat. In Britain, Prime Minister Margaret Thatcher has been seeking to streamline industries to compete more effectively in world export markets.

Despite painful adjustments, Britain's firms have seen their exports decline. Without the benefits of North Sea oil, the country would face a severe balance of payments crisis.

Moreover, the Confederation of British Industry has said that British firms have not shared in a gradual recovery in retail sales and that lower labor costs abroad still provide an edge to imports.

The Thatcher government, like others in the European Community, is hoping that a general improvement in the world economic picture, fueled perhaps by a sudden drop in interest rates, will brighten the fortunes of a more efficient mix of British industries and create new jobs for the country's 3.4 million jobless.

IMF officials say that the traditional uses of government spending to pump economies out of recession have been eroded by the predominant role the state already plays in most European economies.

In the Netherlands, for example, government spending accounts for nearly 70 percent of the gross national product, a proportion that virtually nullifies any further state aid that could inject growth into the economy.