U.S. lawmakers from Michigan have introduced legislation to expand a government loan program to help auto makers rebuild plants to make fuel-efficient vehicles.

The bill would make available $50 billion in low-cost loans to auto makers, doubling the current funding level for the Energy Department program. The bill was introduced by a bipartisan group of 29 U.S. House members, nearly half of them from Michigan, where auto makers such as General Motors Corp. (GM) and Ford Motor Co.(F) plan to use the money to speed the development of advanced-technology vehicles like GM's electric car, the Chevrolet Volt.

President Barack Obama has previously called for doubling the amount of funds available under the program.

"It is vital that the federal government be a full partner to the domestic auto industry's efforts to build the cars of the future," Rep. Sandy Levin, D-Mich., said in a statement Tuesday.

Levin pointed out the Energy Department has received applications for more funds than are currently available in the program, and added, "We need to move quickly to ensure that all eligible investments are able to participate."

The loan program was authorized in a 2007 energy bill that ramps up fuel-efficiency standards for cars and light-trucks. Auto makers seeking the funds must produce plans for the production of fuel-efficient vehicles and meet other requirements.

-By Josh Mitchell, Dow Jones Newswires; 202-862-6637; joshua.mitchell@dowjones.com