Jails have become warehouses for poor and mentally ill people who are unable to post bail for minor infractions such as parking violations or shoplifting, according to a report published Wednesday by the Vera Institute of Justice.

The report, titled “Incarceration’s Front Door: The Misuse of Jails in America,” asserts that while public criticism has focused on the problems of overcrowding in state and federal facilities and the inhumane treatment of some inmates, the jail system is also in need of scrutiny and reform.

“Too often we see ordinary people, some even our neighbors, held for minor violations such as driving with a suspended license, public intoxication, or shoplifting because they cannot afford bail as low as $500,” Nicholas Turner, president and director of Vera, wrote in the report.

Turner said he was “jolted” by the sheer amount of Americans jailed simply because they did not have the financial means or mental capacity to post bail.

“I was startled by the numbers of people detained for behavior that stems primarily from mental illness, homelessness, or addiction,” he said.

An estimated 731,000 people are held in some 3,000 city and county jails in the U.S. on any given day, not to be confused with the state and federal prison system where convicted criminals serve their sentences. Admissions to jails nearly doubled since 1983 to reach 11.7 million per year in 2013, the report said. That’s nearly 19 times the number of annual prison admissions.

Furthermore, three of every five people in jail have not been convicted of a crime, but are being held because they are too poor to post bail while their cases are processed, the report said. The majority of them — 75 percent — are in jail for non-violent traffic, drug or public order offenses such as public drunkenness or driving with a suspended license, the report added.

In New York City, for example, nearly half the jail cases booked are for misdemeanor charges or less, the report said.

Earlier this week, civil rights groups filed lawsuits on behalf of 20 residents of two Missouri towns, alleging that local courts had been attempting to boost the cities’ coffers by jailing people in “deplorable conditions” for minor offenses.

The lawsuits claimed the plaintiffs were, in effect, being held in “debtors’ prisons” where they were being ransomed back to their families and friends for arbitrarily set fines.

As a result of such practices, Vera’s report said jails are increasingly serving as clearinghouses for the disadvantaged, but don’t often provide drug or mental-health treatment to prevent recidivism.

The report notes that 68 percent of all people in jail have a history of abusing drugs or alcohol. Moreover, inmates are four to six times as likely to have a serious mental illness such as bipolar disorder or schizophrenia than the general population.

In fact, 60 percent of jail inmates have reported symptoms of mental health problems within the 12 months before their arrest, according to the Bureau of Justice Statistics.

Vera’s report concluded with a call to action for jail reform.

“The misuse of jails is neither inevitable nor irreversible,” the report said. “But to chart a different course will take leadership and vision. … To both scale back and improve how jails are used in a sustainable way, localities must engage all justice system actors in collaborative study and action.”