Lawmakers told concerned residents huddled on the State House steps yesterday they are working to secure debt-relief funds for the struggling MBTA, saying the responsibility to fund the organization falls on Massachusetts.

“The debt of the MBTA is the state’s problem — not the taxpayers’,” said Rep. Carl Sciortino (D-Middlesex).

Sciortino is the lead sponsor of the MBTA Debt Relief Bill, which calls for the commonwealth to provide an annual reimbursement to the MBTA for the money it pays toward its “legacy debt” — funds the MBTA is still paying the City of Boston for the Big Dig — which would amount to about $280 million a year.

“The way it is going now, the T cannot sustain itself,” Sciortino said, “and if the T goes, most of the Boston infrastructure goes with it.”

The bill, filed Jan. 10, has not yet been discussed by the Transportation Committee, said Sciortino’s legislative aide, Daniel Glasser, but he said he expects a hearing soon.

Rep. Elizabeth Malia (D-Suffolk), a bill co-sponsor, told the 40 people at the rally the funding would allow the MBTA to have financial flexibility to focus more on improving efficiency.

According to a Massachusetts Public Interest Research Group fact sheet provided to The Daily Free Press, the MBTA devotes 27 percent of its annual budget – $363 million – to pay off debt, and it is the organization’s largest single expense.

Paying off a debt that reaches more than $8 billion has led to “unrealistic fare hikes,” said T Riders Union organizer Lee Matsueda. In January, the MBTA raised fares on the subway from $1.25 to $1.70 for riders using the CharlieCard and to $2 for people using the CharlieTicket or cash. Bus fares also rose from $.90 to $1.25.

“We want riders of the T to understand that the problem is much more than debt,” Matsueda said. “We have had price increases, and yet our service hasn’t changed.”

Matsueda said despite having to pay higher fares, T riders are still burdened by buses running behind schedule and buses that are overcrowded.

“Transit is a public good, so fix the transit in my hood,” the crowd chanted during the rally.

The rally also kicked off the Union’s “Ride for Your Rights” week, during which members will talk to T riders waiting at stops and hand out wallet-sized guides listing riders’ rights.

MBTA representatives could not be reached for comment last night.