Paris — Socialist President Francois Mitterrand's biggest political problems these days are not with the conservative opposition. They are with his own partners in government, the Communists.
For months, the Communists had been raising their level of protest against the government's economic austerity plan. Last week, the Communists became more strident in criticizing the government's decision to cut employment in the steel industry by 25,000 jobs. Communist leader Georges Marchais marched alongside steelworkers in a massive demonstration to the Eiffel Tower, and later declared, ''we are going in the reverse direction we promised.''
This infuriated President Mitterrand. Saying ''all members must accept their share of the difficulties,'' he called for a rare vote of confidence in the National Assembly.
He received it - but only after a nasty, eight-hour debate in which the Communists continued to express ''their deep regrets'' about the government's policies.
The result still leaves the Socialists and Communists bickering and close to a rupture.
For the Communists, only reflation, combined with a dose of protectionism, can put France on the road to economic recovery. For the Socialists, the market must rule and France must make her industries internationally competitive.
The big question is how much communist sniping Mitterrand will accept. His Socialists have a majority in the National Assembly and don't need the Communists to govern. This means there is no question of Mitterrand changing policy to suit the party demands.
But if the Communists quit the government, they could turn present simmering industrial protest into a wave of strikes inspired by the party-dominated Confederation
Generale du Travail. The Communists could also pick up working-class votes from those disillusioned with the government's present policies. Since many Socialists won with communist votes in 1981, this could dangerously weaken Mitterrand's party in June's European elections and in 1986's legislative vote.
''If the Communists were out of the government, they would make the current problems look like a picnic,'' says Alfred Grosser of the Paris Institute for Political Science.
The Communists are also wary to provoke a break. Participation in the government gives them respectability. They occupy four ministries, transportation, professional training, employment and civil service, and have the power to appoint party members to positions throughout the bureaucracy.
Moreoever, leaving power is a risky political move. When the Communists last broke an alliance with the Socialists in 1977, they were widely charged with opening the path to a conservative victory. Since then, communist support has fallen from 20 percent of the vote to as low as 10 percent. So any support they may pick up from disgruntled Socialist voters may be offset by the bad feelings they cause in their departure.
As this analysis shows, the Socialist-Communist tussle is, above all, tactical. Each side wants to gain political capital by putting the blame on the other.
Mitterrand embarrasses the Communists every time he ties them to a policy in which they don't believe. The Communists looked foolish during the confidence vote, for example, criticizing the steel plan and then being forced to vote for it.
On the other hand, the Communists are positioning themselves well if Mitterrand decides to throw them out of the government. In the past, they have focused their criticism on foreign policy differences - Chad, Lebanon, and especially the Soviet Union.
''It was a disastrous move,'' says Patrick Jarreau, specialist in communist affairs for Le Monde. ''This would have let Mitterrand show that they left the government because they are Soviet tools, not because they promoted economic policies for the working man.''
Recently, the Communists have quieted these foreign policy gripes, focusing instead on the more sensitive and controversial domestic policies. Proving that this tactic hurts much more, socialist complaints have picked up.