Members of a legislative panel on Monday sharply criticized a plan to nearly triple the number of Medicaid and food stamp cases handled by a troubled computer enrollment system.

Under the plan, Health and Human Services Executive Commissioner Albert Hawkins proposed adding about 953,000 elderly and disabled people to the system between December 2008 and September 2009. Some lawmakers and advocates for people with disabilities called that reckless because the state has had problems processing cases in the system as quickly as the federal government requires.

"If this conversion is not totally successful, people will be without services — this is probably the most vulnerable population we have," Colleen Horton of the University of Texas Center for Disability Studies told lawmakers. "It's really unfair to place the burden of the consequences of such a massive, untested conversion" on this group.

The expansion plans for TIERS — Texas Integrated Eligibility Redesign System — comes at a time when the agency is struggling with worker shortages and high turnover. The state has had trouble getting enough workers trained in TIERS, which was designed to modernize the enrollment system.

Several lawmakers said they were surprised to learn of the plan last week from an early copy of Hawkins' testimony Monday to a joint House-Senate committee looking at the enrollment system.

"I'm absolutely shocked and dismayed at what has happened," said state Sen. Judith Zaffirini, D-Laredo, "and cannot believe that there is such an obvious attempt to go counter to what I consider legislative intent."

Texas received federal approval to expand TIERS in a limited manner starting this month, but Hawkins said he won't do so until the commission meets a series of benchmarks.

Hawkins said that the agency is working to smooth the conversion and that he will continually evaluate the conversion plan and will not move forward if there are problems. The bulk of the change, which requires approval from the federal agency that oversees food stamps, is set to begin in March.

"It's not etched in stone," Hawkins said of the plan. "It's the plan to guide our efforts, but we're not going to be bound to it."

Additionally, he plans to expand TIERS to other Medicaid and food stamp recipients in Central Texas and the El Paso and Lubbock areas.

The Center for Public Policy Priorities, which is an advocate for low- and middle-income Texans, warned in a report Monday that the state should halt plans to convert any more cases to TIERS until there are enough trained workers to process applications quickly enough to meet federal standards: 30 days for food stamps and 45 days for Medicaid.

In June, Texas completed more than 70 percent of food stamp applications on time in TIERS — an improvement since January but short of the more than 90 percent that were completed on time in the old system in June. Most public assistance enrollment in Texas is still processed using the old system.

Kalese Hammonds of the Texas Public Policy Foundation, which is an advocate for limited government, told lawmakers that delaying TIERS expansion is not the solution — in part because of what keeping two systems is costing taxpayers.

The state spends $1.6 million a month to maintain the system that TIERS was designed to replace, agency spokesman Geoffrey Wool said.