A joint investigation by ABC News and the Center for Public Integrity found that the Department of Housing and Urban Development has struggled to combat theft, corruption, and mismanagement in the more than 3,000 public housing agencies nationwide it funds, and particularly inside the 172 that HUD considers the most troubled, according to an article Wednesday at the center's website by Brian Ross, Ani Patel, John Solomon and Laurel Adams.

"The problems are widespread," the article said, "from an executive in New Orleans convicted of embezzling more than $900,000 in housing money around the time he bought a lavish Florida mansion to federal funds wrongly being spent to provide housing for sex offenders or to pay vouchers to residents long since dead."

"We're failing these tenants, we're failing the taxpayers," said Kenneth Donohue, who recently retired as the HUD inspector general in charge of rooting out waste, fraud and abuse from the federal housing program.

"I think we're doing a good job. More importantly, I think a vast majority of housing authorities across this nation are doing a good job," Assistant Secretary Sandra Henriquez said in an interview.

One of the public housing authorities Henriquez cited for superior performance: Philadelphia. It has long been praised by HUD as a model agency, supposedly far removed from the "troubled" class of housing agencies.

But investigations last summer uncovered allegations that the then-Philadelphia Housing Authority's executive director had spent lavishly on parties that included belly dancers, and had used more than $500,00 in housing authority funds to secretly settle claims accusing him of inappropriate sexual advances with female employees.

"Last fall, after a series of newspaper exposes, the Philadelphia agency's executive director was forced out of his $300,000 a year job running the country's fourth largest public housing authority. And now federal investigators have opened their own probe," the article said.

The joint investigation by the Center and ABC, however, found allegations of mismanagement spread across the country.

For instance, the article continued, "HUD's inspector general discovered that one senior official - Elias Castellanos, chief financial officer of the long-troubled New Orleans Housing Authority - used taxpayer money to buy a million dollar mansion in Florida, with a Lamborghini and BMW parked out front. Castellanos was convicted of embezzlement and sentenced to nearly four years in prison, one of 43 housing officials across the country convicted of crimes over the last two years."

Donohue, the former inspector general, said corruption and fraud have flourished at HUD-funded housing agencies because federal officials in Washington have been asleep at the switch. "During Donohue's tenure as chief watchdog, his investigators uncovered some headline-grabbing examples of other mismanagement problems, like an estimated $7 million worth of payments to provide housing vouchers for dead people," the article said.

Investigators also found an estimated 2,000-3,000 registered sex offenders living in subsidized housing, courtesy of taxpayers, in violation of HUD's own rules.