Gov. Phil Murphy on Thursday vetoed legislation that would have created a more generous housing assistance program for thousands of chronically ill and disabled people in New Jersey, saying the measure would have all but written a blank check the state cannot afford.

State Senate President Stephen Sweeney, the bill’s sponsor and a fellow Democrat, quickly assailed the governor’s decision, calling it “a cold act on the coldest day of the year."

Sweeney, D-Gloucester — who often clashes with Murphy — noted how the thermometer dipped into the single digits this week.

“Days like this should be a reminder that there are homeless veterans suffering from PTSD, abused mothers with young children, recovering drug addicts and alcoholics who find themselves out on the street and need our help," Sweeney said.

The bill (S1965) provided up to a maximum of 18 months of “emergency assistance” payments for low-income people, including those deemed unable to work because they are chronically ill and disabled or are taking care of a sick or disabled spouse or child. Any time spent in the program in the prior to seven years ago would not be counted toward the 18-month period, according to the bill.

The legislation earned rare bipartisan support, passing by a 35-0 vote in the state Senate and 70-9 in the state Assembly.

But Murphy said he could not sign the bill into law because the state budget does not set aside what is likely to be many millions of dollars to cover “possibly tens of thousands of households.”

The nonpartisan state Office of Legislative Services described the financial impact as “indeterminate.” Monthly rental stipends range from $600 to $1000 each, according to the office’s fiscal note on the bill.

As of October, the most recent date information was available 3,600 people were receiving emergency assistance.

“While I certainly support the provision and expansion of affordable housing opportunities, I also believe that the long term financial implications of the bill, and other bills that directly affect the state’s finances, must be carefully considered,” Murphy wrote in his veto message.

“Nullifying Emergency Assistance benefits received more than seven years ago in the manner proposed by this bill would clearly trigger an ‘indeterminate’ unbudgeted cost potentially amounting to many millions of dollars,” Murphy wrote.

State lawmakers should discuss the issue during budget negotiations in the spring, the governor wrote. The bill as written “serves as a poor substitute for more stable and reliable housing support,” the veto message said.

Senate Democrats pushed back on Murphy’s suggestion that the program was too expensive. The existing program serving 3,600 households a month costs $58.1 million in state and federal dollars, according to the current state budget, so even if the program was to grow by a third, that would amount to another $20 million, aides said.

“I am disappointed and deeply concerned that we have failed those in need today,” said Senate Majority Leader Loretta Weinberg (D-Bergen). “Those who are experiencing hard times need a helping hand and the assistance of others. It can make the difference in their ability to overcome the challenges in their lives and live with dignity.”

Murphy is the second governor to veto the bill. Former Gov. Chris Christie, a Republican, took no action when it was sent to his desk before he left office last year, allowing the bill to expire.

The bill was sponsored after Christie attempted to close out two emergency housing assistance programs in 2015, a move that would have upended the living arrangements of 3,000 people. The program, though designed to be temporary, has been renewed by prior administrations because people reliant on welfare and permanent disability checks struggle to find affordable housing in a high-cost state like New Jersey.

Housing and Community Development Network of New Jersey President and CEO Staci Berger called the veto “heartbreaking and unconscionable.”

“It’s baffling that the governor would cut off this lifeline for the small number of people who need temporary help the most. These are New Jersey residents who are already the most vulnerable and cannot be employed,” Berger said.

Susan K. Livio may be reached at slivio@njadvancemedia.com. Follow her on Twitter @SusanKLivio. Find NJ.com Politics on Facebook.