By Mark Abrams

PHILADELPHIA (CBS) — An audit released by the Philadelphia city controller’s office shows the city is owed nearly $50 million for ambulance services for last year, and nearly twice that amount for reimbursements it will never see because of limits by state, federal, and health insurance contracts.

City controller Alan Butkovitz says a review of ambulance billings by the city for 2011 shows it only collected $34 million of the $82.5 million it billed — about 42 percent.

But Butkovitz says there’s an even more disturbing statistic the audit uncovered:

“In fiscal year 2011, there was more than $97 million of potential revenue that was either not billed or was written off. Most of this revenue, $78 million, cannot be collected because it is considered disallowable either through Medicare, Medicaid, or Independence Blue Cross.”

Butkovitz says the reimbursement caps result in the city being paid between 13 and 19 cents on the dollar for services that are billed at $950 for “basic” life support services or $1,050 for “advanced” life support services.

The controller says the city needs to press state and federal lawmakers for increases in the Medicaid and Medicare reimbursements or risk running an unsustainable ambulance service in the years ahead.