The National Council of Churches has called for radical changes in this country's criminal justice system.

Decriminalization of certain "victimless" crimes, "drastic reductions" in the use of imprisonment, and proposals to eliminate discrimination by race, sex or class in law enforcement are amoung the measures called for in a policy statement adopted by the council's governing board at its semi-annual meeting here.

The lengthy statement blames most crimes on poverty and adverse social conditions.

"The very existence of the poor and oppressed may be evidence of injustice," the statement says, adding that "failure to do justice is the chief 'crime,' the primary offense of the community as a whole."

Unjust social structures, the statement says, "lead to concentration of economic wealth and political power in the hands of a few, leaving the majority poor and powerless . . . The Bible is quite clear about the sources from which the corruption of justice ordinarily springs: greedy disregard for God's justice that accompanies the grasping of power."

Churches have long been involved in prison reform. Eighteenth-century British Quakers began a movement that eventually eliminated debtors' prisons and helped to improve the harsh prison conditions of that era. Today, numerous evangelical Christian groups work to convert prison inmates to Christianity.

Others, in response to the New Testament entreaty to care for those in prison, carry out a range of programs, from prison chaplaincies to rehabilitation services for ex-offenders.

The council's 22-page policy statement, however, is the most comprehensive evaluation of the criminal justice system produced by a religious group in recent years.

The statement produced extensive debate among representatives of the 32 Protestant and Eastern Orthodox denominations that belong to the NCC. Discussions focused more on theological nuances than on questions of penology and criminal law. In accord with NCC rules, the statement was first debated at the board's meeting last spring before its second reading and adoption here.

In general, the statement argues for less aggressiveness on the part of the criminal justice system, which, the statement maintains, more often than not tends to "compound and aggravate" crime problems.

"The system suffers from unrealistic expectations that it can control crime, compel lawful behavior and alter personal values and attitudes," the statement says. It maintains that the legal definition of what is criminal is "often rooted in cultural values, and behavior labeled 'criminal' frequently is conditioned by social and economic inequities."

The church group argues that "most persons in the general population have committed offenses, a substantial portion so serious that they could have resulted in prison terms had they been apprehended, arrested and convicted." But in practice, the statement continues, disproportionate numbers of the "socially underprivileged" are caught, punished, and labeled as criminals.

"While there are no significant correlations between racial composition and crime rates, there is a very high and positive relationship between racial population and incarceration rates," the statement says.

The council also charges that there is "widespread use of the criminal justice system to suppress nonviolent political dissent, to cope with social problems and to provide cheap labor."

Victims of crime should be cared for, the church group maintains, "and treated with respect, not stigmatized." It also urges that victims and perpetrators of crimes "should have a significant voice and role in negotiating the disposition of criminal complaints, with appropriate safeguards against vindictiveness and intimidation."

Prison sentences should be imposed, the statement contends, only when it can be demonstrated that "no acceptable alternative exists."

The church body suggests that fines, court-ordered service to the community, restitution to victims and probation be used more than prison sentences.

Capital punishment is unequivocally rejected in the statement. Pre-trial detention should be used only "to protect society and the accused from seriously harmful conduct," the church statement says.