France's Socialist Party refused today to continue talks with its Communist political allies on a joint campaign platform.

Socialist leader Francois Mitterand told reporters that his party would wait until Monday to decide whether to continue the talks, which were effectively suspended last night when the Movement of the Left Radicals walked out of negotiations because of Communist demands for sweeping economic changes if the left comes to power.

The Communists called for a meeting to resolve the dispute among the Socialists - France's largest party - the Communists and the minor party in the alliance, the Left Radicals.

The three parties agreed in 1972 on a platform known as the "Common Program," and their alliance is currently favored by public-opinion polls to win the National Assembly elections scheduled for March.

French political analysts say that the prospect of displacing the conservative-centrist coalition that has ruled France for 20 years is tempting for the leftist parties, who may be trying to wring maximum concessions from their partners before agreeing to a joint platform.

But the mood among leftists was somber today. Socialist Party officials who previously predicted an easy resolution of the problems with the Communists were speaking in private of the possibility of a complete rupture.

The first day of a scheduled two-day "summit" of leaders of the three parties broke up in disagreement yeaterday when the Left Radicals rejected Communists demands that hundreds of medium-sized manufacturing firms be added to the list of nine major industrial groups and banking concerns targeted for nationalization in the 1972 platform.

A renewed public appeal from Communist leader Georges Marchais for resumption of talks Friday morning was ignored at separate news conferences by Mitterrand and by Left Radical leader Robert Fabre, whose party commands 3-to-4 per cent of the national vote, a bloc that would be vital in the assembly elections.

In a letter to Marchais released publicly by the Socialists Mitterrand affirmed that he is ready "at any time to resume the discussions" on a platform.

But he added that the party's executive committee would not meet until Monday to discuss the socialists' position on the Left Radicals' walkout.

The Paris stock exchange, moribund for most of the year as the prospects of a leftist victory increased, rose rapidly as news of the crisis within the leftist alliance spread.

Gaullists and supporters of President Valery Giscard d'Estaing praised the Left Radicals' walkout and reiterated that they would be welcome in the governing coalition.