France's quarrelling leftist parties exchanged invitations to renew political cooperation today, but mixed them with mutual accusations of bad faith and demands for concessions.

In a letter released to the press, the Socialist Party formally invited the Communists to resume talks on a joint leftist electoral platform. The talks broke up last week in a dispute that threatens to tear apart the electoral alliance of the two large leftist parties and the minor party of Left Radicals.

Neither the Socialist statement nor a Communist call for new talks that preceded it proposed any specific steps for breaking the deadlock. Moreover, leaders of the parties reterated that they would not budge from their conflicting stands of nationalizing French industry.

Both parties appeared to be digging in for a tense seven-to-14-day period of testing each other's resolve and strength. The executive committees of the two parties are not scheduled to meet before next Wednesday.

While public pressure campaigns aimed at producing maximum concessions are mounted, private contacts will be held to arrange a negotiations summit for a last-ditch effort to patch together an agreement, informed French and diplomatic sources now predict.

The sources pointed out that while the Socialists and Communists have been hurling criticism at each other, they have refrained from unleashing their followers in the trade unions in what would be an all-out public confrontation that could push the dispute beyond repair.

The Gaullists and centrist forces of President Valery Giscard d'Estaing also have began to give their first public responses to the dispute, which appears to be seriously harming the strong prospects the leftist alliance had of winning a majority in National Assembly election next March.

Gaullist leader Jacques Chirac insisted in a speech to his party that his strategy of lumping the Socialists and Communists together as a "red peril" for France was unaffected by the split of the leftist alliance. While welcoming the support of the non-Marxist Left Radical voters, Chirac said he continues to strongly oppose any efforts to the left, and woo moderate Socialists.

This leaves Chirac without a clear strategy of attack for the moment and once again puts him at odds with Giscard and Prime Minister Raymond Barre. Barre suggested yesterday in a message to the Gaullists that "the French political landscape has been changed" by the split. Giscard has been betting that wooing the Socialists would be more successful than hammering them in Chirac's way.

Predicting that the three leftist parties would end their quarrel and go to the March elections with a joint electoral platform.Socialist leader Francois Mitterrand vowed at a press conference yesterday that his party would never make a deal with Giscard's supporters. He said his party would honor its commitment to back Communist or Left Radical candidates in regions where Socialists could not win, even if there is not a joint leftist electoral program.

While the Socialists emphasized their efforts to keep the alliance alive, Communist leader Georges Marchais devoted a lengthy speech at a large public rally last night to attacking the Socialists for "reneging on their commitment to economic changes. He accused Mitterrand of "talking about opening the door to negotiations while in fact closing it."