The massive indebtedness, poor productivity and inefficiency of Italy's vast state-owned industrial sector has reached so critical a point that some economic experts here are convinced that the risk of a major bank crisis now exists.

Critics of the "state participation" system that began in the 1930's and stimulated economic development here in the 1950's blame political pressures, poor management and a recent emphasis on industrial "rescue" operations for a deepending crisis that recently has been aggravated by Italy's general economic problems.

But the weakness of the state sector, which employs 750,000 persons or 10 per cent of Italy's industrial workers and controls about 45 per cent of the total turnover of this country's industrial sector, now appears to have gotten out of control.

According to some sources, the total indebtedness of Italy's state-owned industry has probably reached the $22-billion-dollar mark. A recent survey released by the Milan "Mediobanca" shows that 178 state-owned firms ran losses of almost $1.5 billion in 1976 alone compared to losses of $204 million accumulated by another 617 private companies.

Most, but not all, of the debt is carried by Italian banks. They stand to lose, not only from defaults on the state industrial loans, but from losses on individual loans and withdrawal of deposits by the workers who have lost or will lose their jobs in the crisis.

The major collapse, which some economists here have termed a scandal, involved the dissolution last month of a major state mining and metals conglomerate - often referred to as "the state garbage-dump - that in less than six years had run up debts of over $1 billion.

The conglomerate, called EGAM, was the fourth largest state company, including 52 separate companies and employing a total work force of 35,000, whose relocation is expected to cost the state $33,000 for every former employee.

EGAM's president, Mario Einaudi, who resigned in June 1975, was a political employee of the ruling Christian Democratic Party. His management of the company, which involved buying up a series of bankrupt firms that otherwise would have gone out of business, has been described by economists of all political persuasions as at best inefficient and at worst corrupt.

Late this spring another "scandal" erupted when the country's largest state holding company, the Institute for Industrial Reconstruction (IRI) - which itself has run up cumulative debts of about $20 billion - decided to scrap a long-projected plan for the construction of a fifth Italian steel center in Gioia Tauro in southern Italy.

IRI's decision came when top management realized that at current costs the completion of the center would run as high as 267 million lire, or $294,000 for each of the 7,500 jobs created.

Originally decided upon because of strong political pressures following violent riots in nearby Reggio Calabria in July 1970, the projected center has also now been termed "uneconomic" because of the steadily dropping demand for steel that is now reportedly causing Italsider, the state steel company, to lose about $1.7 million daily.

In the meantime, however, as much as 230 billion lira, or $253 million, may have been spent on infrastructures at Gioia Tauro whose full potential may now never be used.

Last week it was announced that another IRI-owned company, Unidal, which runs Italy's two biggest confectionery factories, Motta and Alemagna, and employs 7,500 persons, will have to be liquidated.

Other discouraging figures are the $4.5 billion deficit run up by Italy's publicly-financed highways, or "autostrade", and the $2 billion of debts accumulated by Montedison, the partly-state-owned giant chemical conglomerate.

And if all this wasn't enough, the defects of the system were further dramatized last month when the newly appointed president of Agip, the state oil company, resigned because of inefficiently within his own firm as well as that of its parent holding company, the national hydrocarbon's agency, ENI. The president, Egidio Egidi, said in his letter of resignation that he could not cope with a situation in which "an internal balancing act ended up by paralyzing everything and delaying all decisions.

With the parliament clamping down in recent years on allocations for an increasingly non-productive system, the state companies have been turning to high-interest loans from Italy's banks, many of which are themselves state-owned or publicly financed.

The crisis has deepened because of the general recession that has affected the entire business sector here. The potential for widespread bankruptcies among state companies threatens the stability of many Italian banks. This would be particularly ironic since Italy's state participation system was born during the depression when the country's commercial banks, then co-owners of most major firms, were saved from default by government purchase of their stocks and the creation of the Institute for Industrial Reconstruction.

The former governor of the Bank of Italy, Guido Carli, now president of the NationaL Manufacturers' Association, said recently that "the crisis . . . is primarily a crisis of responsibility." He criticized the fact that "the heads of public corporations are evalusted not on the basis of their efficiency but on their party loyalties."

And Eugenio Peggio, one of the Communist Party's top economists, said last week that "the system cannot be revitalized until state company directors, chosen on the basis of their managerial abilities, are given the responsibility to make choices and the chance to sink or swin by them."