NATIONAL GRID and the 1,200 steelworkers the company has locked out of work battled each other outside the negotiating room on Wednesday, with the union pressing state regulators to crack down on the utility for doing shoddy repair work and the company running newspaper ads defending its contract offer.

The company said in a full-page ad in the Boston Globe that its five-year offer includes increases that will boost the current average employee salary from $120,000 a year, including overtime, to $137,000; a no-layoff guarantee to all employees with more than five years of service; and a 10 percent increase in pension benefits for current employees. The contract offer would also put new employees on 401K plans with a 3 to 9 percent company match.

Union officials say the company’s proposal would reduce health care benefits for current employees and retirees and provide less sick time and life insurance to new employees. “The tactic of hoping older employees will sacrifice the benefits of new hires is a disgraceful attempt to drive a wedge between employees,” the union said on its website.

A National Grid spokeswoman confirmed the company is asking employees to pay more for health insurance. She said members of the steelworker locals currently pay no deductibles and no co-insurance, and would start paying both under the new plans. She said the company’s other unions in Massachusetts and Rhode Island agreed to similar plans last year.

Both sides in the labor dispute are playing hardball. The lockout, which began June 24, appears to be an attempt by the company to pressure the union into accepting the new contract terms. The union has responded by raising safety concerns about the replacement workers doing their jobs, a move that gained significant traction in the wake of fires and explosions along gas lines in the Merrimack Valley on September 13.

A preliminary investigation of the Merrimack Valley incident by the National Transportation Safety Board blamed the fires and explosions on over-pressurization of pipes in the area. The cause appeared to be a faulty work plan for a pipe replacement project, but the incident has fanned fears about the danger of natural gas.

John Buonopane, the president of one of the steelworkers locals, said the state Department of Public Utilities only began investigating the union’s complaints about National Grid after the September 13 incident involving Columbia Gas in the Merrimack Valley. “We’re very concerned about how National Grid is operating,” Buonopane said after a meeting on Wednesday with DPU officials. “This is really about public safety. We want people to know how serious our jobs are.”

National Grid discovered pipe over-pressurization in part of Woburn on October 8 and shut down service to 300 homes temporarily while the situation was addressed. In the wake of that incident, the Department of Public Utilities ordered Grid to halt all work across its entire service territory except for emergency and compliance work.

That order, combined with calls from a number of elected officials, including Gov. Charlie Baker, to end the walkout, has put additional pressure on National Grid to reach a deal with the steelworkers. The company has also faced financial consequences, as its costs have trended up slightly while gas leak repairs and new gas hookups have declined.

The company said it is eager to do reach a deal with its unions and is prepared to meet more regularly, but the two sides have yet to establish a more frequent meeting schedule. Grid officials say the meeting schedule is dictated by the unions.

“The ad is just a diversion from recent events,” said Buonopane, referring to National Grid’s ad in the Globe. “I think they forgot that they locked us out. They did it to pressure us to take something they wanted us to take.”