Life is becoming very difficult for France's Communist Party. Its problem is whether to remain a quiet partner in the ruling French left-wing coalition or to seek wider support by capitalizing on workers' discontent with President Francois Mitterrand's increasingly tough economic policy.
Although the Communists have no rivals for keeping their internal affairs secret, there is no doubt the party is increasingly split between its two options. The dilemma is made all the more painful because the party's electoral strength has been declining steadily and its trade-union arm is losing ground.
The pressures being felt by the party leadership became apparent this week when the government went to the National Assembly for approval of an austerity package which would slash consumer spending, increase taxes, and cut economic growth to close to zero this year. This is light-years away from the doctrine propagated by Communist economists, who call for increased consumer spending to get French industry moving.
The Communist leader in the National Assembly, Andre Lajoinie, made the party's distaste for the government measures clear during the four-day debate on the economic program in Parliament. To speed up the implementation of the austerity package, the government proposed to act by decree instead of going through a full debate on each measure. The Communists immediately said they would not approve the decree procedure unless the austerity measures were scaled down.
This would not have brought defeat for the government, since the Socialists have an overall majority in the assembly. But it would have been the biggest split between Communists and Socialists since President Mitterrand first took Communist ministers into the government in June 1981.
While Mr. Lajoinie was talking tough in Parliament, party boss Georges Marchais spoke to reporters about the need for the Communists to act ''autonomously.'' Party branches in Paris received copies of a statement written by anonymous Communist officials denouncing government policy. The party newspaper, l'Humanite, struck a jaundiced note in writing about the program of Prime Minister Pierre Mauroy and Finance Minister Jacques Delors.
Eventually, after winning a few of their demands for tax concessions to low-income people, the Communists fell into line Tuesday and voted for the decree procedure. The wing of the party that supports continued participation in the government - led by Transport Minister Charles Fiterman - had won the day. Mr. Lajoinie, who is generally seen as advocating a break with Mr. Mitterrand, retreated - but to fight another time. Mr. Marchais remains balanced between the two factions, as he has been for months.
Given all this, it is not surprising that the Communists are a declining force in French politics. Fourteen years ago, their candidate was able to win 20 percent of the vote in the presidential election (compared to 5 percent for the Socialist candidate). But the rise of Mr. Mitterrand and his Socialist Party was accompanied by a steady decline in Communist popularity. In part this is because Communist voters have crossed over to the Socialists. It is also because the party has appeared increasingly out of touch with changes in French society and has been embarrassed by its links with the Soviet Union, particularly over Poland and Afghanistan.
Joining the Mitterrand administration in 1981 allowed the Communists to show that members like Mr. Fiterman could be efficient departmental ministers. But the party's popularity in the country went on declining. It is now reckoned to be less than 15 percent nationwide.
Municipal elections in March saw the Communists beaten in several major cities they previously controlled and even losing ground in their traditional strongholds in the ''red belt'' suburbs of Paris. Paralleling this political decline have been the losses of the Communist-led Confederation Generale du Travail (CGT) in recent trade union elections. The CGT is becoming increasingly torn between its anger at the austerity measures and its policy of not causing too much trouble for a government that contains Communist ministers.
The party's central committee is expected to thrash out the current contradictions in Communist policy when it meets next week. The major question is the future of Mr. Marchais. His political demise has been suggested ever since his poor performance in the 1981 presidential election in which he won 15 percent of the vote. He has shown considerable staying power, however. Replacing him would imply that the party had made up its mind between the two courses open to it.