Two major advocacy groups for the homeless have ranked Los Angeles as the "meanest" city in the US, citing a Skid Row police crackdown they say has criminalised poverty and homelessness there.

LA's so-called Safer City Initiative was singled out in the groups' report as the most egregious example of policies and practices nationwide that essentially punish people for failing to have a roof over their heads.

Others include making it illegal to sleep, sit or store personal belongings on sidewalks and other public spaces; prohibitions against panhandling or begging; and selective enforcement of petty offenses like jaywalking and loitering.

Such measures are widespread in the face of a deep economic recession and foreclosure crisis that have increased homelessness over the past two years, according to the National Law Centre on Homelessness & Poverty and the National Coalition for the Homeless.

Their report examined laws and practices in 273 cities across the country, with Los Angeles topping the list of the 10 "meanest cities" for what the study called inhumane treatment of homeless. A previous report, issued in early 2006 before the crackdown began, ranked LA as the 18th meanest.

Under the Safer City effort, thousands of LA's most destitute residents have been targeted for harsh police enforcement, routinely receiving tickets for minor infractions such as the failure to obey crossing signals.

As a result, the study says, many are jailed and end up with a criminal record that makes it more difficult for them to find a job or gain access to housing.

A spokesman for Mayor Antonio Villaraigosa issued a statement dismissing the report as "short-sighted and misleading".

Los Angeles officials have touted their Safer City effort for sharply curbing serious crime in Skid Row, a 50-block downtown area inhabited by the biggest concentration of homeless people in the country. "The city's first priority is to protect our most vulnerable residents from violent crime," the mayor's statement said.