A Cobb County couple whose lawsuit over their daughter’s fatal crash exposed problems with faulty ignition switches wants to throw out their settlement with General Motors on allegations the automaker hid evidence and allowed its employees to lie about it.

The extraordinary decision by Ken and Beth Melton led them to file a new lawsuit Monday in Cobb County State Court in which they accuse GM of negligence, fraud and concealment.

“I’m hurt emotionally they’d be so desperate not to disclose all the information,” Ken Melton said. “After the Senate hearings (in April) it was amazing how much information came out. I feel like I have been lied to. … This is our daughter’s life we’re talking about … my daughter’s life, which I loved dearly.”

Brooke Melton died March 10, 2010, as she was driving up Ga. 92 in Paulding County to meet her boyfriend and celebrate her 29th birthday.

On the way, her 2005 Chevy Cobalt’s ignition switch failed and her engine turned off, leaving the pediatric nurse without power steering and with greatly reduced brake power. She lost control, crossed the center lane and was struck by another car. She suffered a catastrophic brain injury and died that evening.

In 2011, her parents filed suit against GM and last September reached a settlement, the amount of which remains confidential. Their case has been credited by auto safety experts with exposing that GM knew about the ignition-switch defect for more than a decade and resulting in the recall of more than 1.6 million GM vehicles.

The Meltons’ new lawsuit alleges that, during the course of the previous litigation, GM fraudulently denied that any employee authorized or even knew of any design change in Cobalt ignition switches before Brooke’s deadly crash. It notes that GM lead design engineer Ray DeGiorgio repeatedly testified that he did not authorize or know of any such changes.

But recent disclosures by GM to the National Highway Traffic Safety Administration and to Congress contradict the company’s earlier assertions that GM employees were unaware of any design changes to the switches, the new suit says.

Lance Cooper, the Meltons’ lead attorney, said his clients believe the new lawsuit “is the best opportunity to discover the whole truth about GM’s decision to secretly redesign the ignition switch and why Brooke was never told of this change.” They never would have settled their case when they did “if they had known of the perjury and concealment of critical evidence,” Cooper said.

The Meltons settled their case believing that GM knew nothing about the design switch change, he added. “In other words, they took GM and their lawyers at their word. They now know they were lied to.”

After the recent disclosures came to light, the Meltons asked GM on April 11 to rescind the original settlement.

But GM refused. In response, the company’s attorney, Robert Ellis, wrote the automaker “denies the assertion that GM fraudulently concealed relevant and critical facts in connection with the Melton matter. And GM denies it engaged in any improper behavior in that action.”

On Monday, GM said it stands by that same statement.

The Meltons’ new lawsuit was assigned to Cobb State Court Judge Kathryn Tanksley. She must now decide whether to rescind the settlement agreement and allow the new claims to proceed toward trial. Her decision is expected in the coming months.

If the case does go forward, Cooper said, he may try to get pretrial testimony from GM Chief Executive Officer Mary Barra and the company’s in-house lawyers.