BOSTON — Pressure is growing on National Grid to end a six-month impasse with natural gas workers who remain locked out of their jobs amid stalled contract talks.

Last week, the state House of Representatives approved a bill calling for a new program, paid for by gas and electric companies, to cover unemployment benefits of workers who are temporarily off the job during contract talks. The measure is now before the state Senate, which could take it up later this week or next.

Senate President Karen Spilka, D-Ashland, and Minority Leader Bruce Tarr, R-Gloucester, issued a joint statement Monday calling on National Grid and its unions to break the impasse.

"We believe the two parties can continue negotiations – and they must continue negotiations – while allowing these families to put food on their table, take care of their children’s pressing health needs, and enjoy their holidays together," the statement read. "This process has gone on long enough, and the Senate is prepared to take action if needed."

More than 1,200 National Grid workers have been locked out of their jobs, with no salary or benefits, since June 25 after contract negotiations with union leaders broke down.

National Grid said it has redeployed about 700 contract workers and put 600 supervisors into the field to replace the locked-out union workers.

Many of the locked-out workers face the likelihood of losing unemployment benefits in January if the impasse isn't resolved before then, union leaders say.

Lawmakers have said they hope the bill will force both sides to reach an agreement to end the lockout, which is approaching its seventh month.

Union leaders issued a joint statement on the legislation approved by the House, saying it "offers much needed protections for our workers and safeguards a critical economic lifeline — particularly as National Grid continues to use members’ paychecks and their families health insurance as bargaining tools during these negotiations."

"National Grid has utterly failed to live up to its obligations as a public utility during this lockout, and its lack of urgency is wreaking havoc on residents, businesses and communities across Massachusetts," read the statement from United Steel Workers locals 12003 and 12012.

New benefits program

The House bill establishes a new benefits program for gas and electric workers who are unemployed during collective bargaining negotiations because of an employer’s lockout. Costs would be assessed on the employer who has locked out its workers.

The legislation also prevents utilities from passing on costs of the program to ratepayers.

House Speaker Robert DeLeo has called the lockout a "negotiation tactic" that is being subsidized by taxpayers and the state's unemployment insurance fund.

"The commonwealth cannot sit idly by while a large, international conglomerate volitionally locks out employees in a transparent effort to enhance its leverage in a negotiation, while passing on the cost for this misguided strategy to the taxpayers and ratepayers,” DeLeo told reporters ahead of last week's vote.

Gov. Charlie Baker, a Republican, also has called for an end to the lockout and expressed support for legislation aimed at pressuring both sides to reach an agreement.

Another proposal, which hasn't been voted on by either the House or Senate, would require utilities to continue to pay health insurance premiums for locked-out workers.

The National Grid dispute has gotten added attention from state leaders following the Sept. 13 gas fires and explosions in the Merrimack Valley, which involved thousands of homes and businesses served by Columbia Gas.

The state Department of Public Utilities has imposed a moratorium on natural gas work by National Grid and Columbia Gas while the state reviews gas pipeline safety issues.

On Tuesday, the Legislature's Joint Committee on Telecommunications, Utilities and Energy holds a hearing at the Statehouse on the safety of the state's natural gas pipeline system. Lawmakers are expected grill representatives from Columbia Gas/NiSource on the response to the gas explosions, as well as National Grid officials on the stalled contract talks.

Meanwhile, Attorney General Maura Healey has asked state regulators to look into whether National Grid is complying with the state's safety and quality standards.

The company expected to return to the negotiating table with union leaders later this week. Both sides have pledged to meet regularly until an agreement is reached.

Christian M. Wade covers the Massachusetts Statehouse for The Salem News and its sister newspapers and websites. Email him at cwade@cnhi.com