Communications Workers of America officials contend that Verizon has failed to fund the upkeep of its copper phone lines that still serve eight million customers and called Wednesday for Pennsylvania regulators to investigate.

The CWA also sent letters to regulators in Delaware and Virginia, seeking investigations. The union is expected to eventually send one to New Jersey regulators.

The union criticism comes as Verizon and the CWA are locked in thorny contract negotiations that include issues related to Verizon's commitment to its hybrid network of copper and high-speed fiber-optic lines, or FiOS.

The CWA would like Verizon to wire its entire multistate area for FiOS, a capital investment that would support CWA jobs.

But Verizon has said it will soon halt its FiOS expansion, leaving many areas with only copper lines. Without proper investment, the service quality in those copper-line areas will deteriorate for customers and could force them into a wireless service, the CWA said.

"They have put virtually nothing into their copper network over the last seven years," Debbie Goldman, the CWA's telecom policy director in Washington, said on Wednesday. She said Verizon has been "in effect" abandoning its copper lines by starving them of funds.

Verizon disclosed a $200 million investment in its copper phone lines between 2008 and 2014 in a July letter to the Federal Communications Commission, Goldman said.

The $200 million is a fraction of the $50 billion the company has invested in its fiber-optic network between 2008 and 2014, the union says.

Nils Hagen-Frederiksen, spokesman for the Pennsylvania Public Utility Commission, said on Wednesday that the agency received the CWA letter and was reviewing it.

Verizon blasted the CWA's calls for investigations into its maintenance of and investment in copper phone lines.

"It's a bargaining gimmick, and their assertions are nonsense," Verizon spokesman Rich Young said. "To say that we are avoiding network investment is ludicrous, and we are quite confident that any investigation will find that the CWA's assertions are flat-out wrong."

Young said that Verizon invested $1 billion into its network in Pennsylvania in 2014 and $547 million into its network in New Jersey in 2014.

Young said he could not comment directly on the $200 million.

An Inquirer business story in early June showed that even as the FiOS rollout was ending, many New Jersey neighborhoods don't have the high-speed fiber-optic lines running to homes.

Verizon contracts with about 39,000 members of the CWA and the International Brotherhood of Electrical Workers expired Aug. 1. The two sides continue to negotiate in Philadelphia and Rye, N.Y.