Portuguese Prime Minister Mario Soares moved to avert a government crisis today after the resignation of Carlos Mota Pinto as leader of the Social Democratic Party cast doubt on the survival of the 19-month-old coalition.

Soares, who heads the Socialist Party, urged Mota Pinto, who is also deputy premier and defense minister, to ensure government stability by remaining in the Cabinet at least until the leadership crisis within the junior coalition party is resolved, according to Soares' office. It said maintaining the coalition of Socialists and Social Democrats in office is essential to economic recovery.

Mota Pinto quit as president of the Social Democratic National Council yesterday after calling for a vote of confidence in his leadership following persistent criticism from rebel party factions. He said the two-vote majority he received from the council did not constitute the "clear support" he had sought.

Mota Pinto has left his continuation in the Cabinet to the discretion of the government and his party. Social Democratic officials said a National Council meeting this weekend would appoint a caretaker leadership to assume the party's goverment responsibilities until a special party congress called for March could elect a new leader.

Former finance minister Joao Salgueiro and former parliamentary affairs minister Marcelo Rebelo de Sousa head the two Social Democratic factions whose "damaging and persistent opposition" Mota Pinto said forced him to resign.

The factions have also been critical of what they see as Mota Pinto's failure to bring about more radical economic reforms. The Soares government has lowered Portugal's balance-of-payments deficit from $3.2 billion to below $700 million in less than two years -- but at the cost of a harsh domestic recession.

Social Democratic hard-liners want tougher measures, to streamline the country's vast, heavily indebted public sector. Mota Pinto supports such proposals but has made it clear he has had to compromise to maintain the coalition.