Political terrorism in Italy has become so widespread that a trial of 53 alleged terrorist was postponed this week after several jurors were so intimidated by threats that they declined to serve.

The postponement Tuesday of the trial of the top leaders of the Red Brigades that began operations in 1972 appears to have deeply shocked press and public opinion here. Commentators and political spectrum as well as government spokesmen termed the suspension a victory by the forces of subversion.

"We've come to a sorry state if terror is so widespread it prevents the court from putting a jury together," said an official of the small Republican Party.

The postponement was dramatized by the murder last week of Fulvio Croce, 76, the president of the Turin Bar Association by Red Brigade Killers.

Croce's murder and the kidnaping of the dean of the Rome University law school by unknown assailants the same day were interpreted as attempts to prevent the holding of the trial and thereby demonstrate the collapse of the machinery of "bourgeois justice."

The first reaction to the murder by bar association officials was, in fact, decision to deny legal representation to the 53 defendants that would have menat holding up the trial.

This obstacle was overcome when some 400 Turin lawyers volunteered privately to act as court-appointed counsels so justice could take its course. The response of the extremists was a barrage of threatening phone calls aimed primarily at top magistrates, doctors and police officials that spread panic through the city and prompted four of the eight selected jurors to claim illness and refuse to appear in court.

The trial is not expected to be held until next year and politicians and judicial experts are considering new regulations that would eliminate jury trials for those accused of terrorist activities.

The Red Brigades, a far-left group which police estimate to have fewer than a thousand members, is accused of numerous robberies, kidnappings, shooting attacks and murders since it emerged five years ago.

The postponement of the Red Brigades trial and a daring jail break Tuesday in Milan by six of Italy's most dangerous bandits climaxed a period of spiraling terrorism and violence that is threatening the minority Christian Democratic government.

Already weakened by its failure so far to deal with continuing inflation, recession and growing disaffection among high school and college students, the government is coming under increasing pressure by the powerful Communists who seek a greater political role.

A series of talks between the ruling Christian Democrats and each of Italy's other major parties began this morning with a three-hour meeting of Christian Democrats and Communist Party officials, the first of its kind in 30 years.

The Communists called he meeting a sign that they were nearing their goal of "national" government that would include all of Italy's six major parties and give the Communists seat in the Cabinet for the first time since 1947.