"The Ministry is actively trying to bury information about what happened in the past," Ms Cooper said. "It has become a grim, hang-in process for our clients."
Judge Carolyn Henwood, speaking in her capacity as the chairwoman of the recently concluded Confidential Listening Service, said the situation was concerning and raised the prospect of vulnerable people being denied access to justice.
"As far as I can tell, throughout the entire seven years the service was operating, some of that litigation has not made any further traction. It's concerning that nothing has been resolved," Judge Henwood said.
She said a recent report exposing ongoing failures in the state care of children showed lessons from the past needed to be learned.
Minister for Social Development Anne Tolley agreed the legal log-jam was unacceptable.
"There is no doubt that some cases are taking far too long to settle through the court system and I acknowledge that this process can be emotional and difficult for claimants," she said.
Mrs Tolley said she had recently introduced a fast-track process, leading to 940 settled claims and $14 million paid out in compensation.