AUGUSTA — Mainers without insurance coverage for prescription drugs would save 20 percent on their pharmacy bills under a bill developed by the state Department of Human Services, Commissioner Kevin Concannon said Wednesday.

Concannon said the bill would direct DHS officials to enter into voluntary rebate agreements with drug manufacturers, similar to discount agreements the manufacturers make with health maintenance organizations and insurers.

The state’s Medicaid and Elderly Low Cost Drug programs already pass along rebates, according to Concannon.

“We are proposing to have the drug companies extend this same rebate to people who pay for their own prescriptions,” Concannon said in a prepared statement distributed by his office.

Under the DHS plan, a drug manufacturer could be designated a “preferred provider” by reaching a rebate agreement with the state.

State officials then would advertise the names of pharmaceutical companies offering the rebates in newspapers and through a publication distributed to doctors around the state.

Doctors could refer to the listings of participating companies before writing prescriptions.

“This important proposal is our attempt to do something about the rising drug costs for people who pay for their own prescription drugs,” Concannon said.

He also said the department’s plan, which has attracted bipartisan sponsorship, would complement rather than conflict with other legislative proposals to expand the Elderly Low Cost Drug Program.

“Approximately 60 percent to 70 percent of Maine citizens have their prescription drugs paid for by a third party, either an insurer or the state’s Medicaid Program,” Concannon said.

“These insurers are able to take advantage of various rebate and financial savings agreements with drug manufacturers.

“We are proposing that the other 30 percent to 40 percent of Maine people, who are largely elderly or people without prescription drug benefit insurance coverage, be able to take advantage of the same system,” Concannon said.

DHS officials said Maine is uniquely positioned to undertake the program because the department is connected electronically to all pharmacies in the state.

Officials said the network would allow the program to be administered without putting a major burden on the pharmacies while promoting convenience for consumers, who could obtain their discounts at the time of purchase.

Retail spending for prescription drugs has passed $80 billion annually, increasing by 11 percent to 14 percent a year since 1995, government figures show.