The Montgomery County Council approved a measure Tuesday strengthening a safety net program for the working poor, but left room to opt out if it decided the extra support was not affordable.

The council voted 9-0 to raise the Working Families Income Supplement, a county payment intended to piggyback onto the federal Earned Income Tax Credit (EITC) for low-income working people. Eligible households can receive tax credits of up to $6,000 a year from the EITC. Maryland allows those households to claim half of their federal credit on state income taxes.

The county had provided a 100 percent match for the state credit but rolled it back during the recession to under 70 percent. The match has risen again gradually and currently stands at 85 percent. The legislation, sponsored by council member Hans Riemer (D-At-Large), commits the county to restoring it fully by 2017. The complete match would mean an extra $124 a year for eligible families, for a total of about $500 under the supplement.

Riemer said these are dollars that matter to the working poor.

“It puts food on the table. It helps people pay bills,” he said Tuesday, adding that research shows the EITC helps the working poor stay employed.

But the modest initiative has had a bumpy ride. Some members contended that it locks the council into an expensive and inefficient way of helping the county’s needy. The 100 percent match will cost an estimated $20 million annually for about 40,000 recipients. In hearings before the Government Operations Committee, County Council President Nancy Navarro (D-Midcounty) and council member Valerie Ervin (D-Silver Spring) said increasing the tax credit could make it difficult for the council to maintain its support for numerous community groups that serve the poor directly.

Amendments sponsored by Riemer allow the council to opt out of the extra expense. They cut from six to five the number of members needed to pass a waiver deferring any rise in the supplement, and they add an “escape clause” that can be invoked if the state increases the amount households can claim on their federal credit.

During brief discussion Tuesday, members said the bill merely codified what the council’s intention has been all along — to raise the match back to 100 percent.

“I appreciate everyone’s spirited advocacy,” said council member Nancy Floreen (D-At-Large) , but she asked: “How is this different from how we do things now?”

The answer from a council attorney was, in essence, it isn’t.