Those who voiced their “growing anger” included the families of Christie Harnett and Nadia Sharif, who were treated at West Lane Hospital in Middlesbrough, where they died by suicide both aged 17, and Emily Moore, 18, who also took her own life after being treated there.
A report previously found 119 failings in the teenagers’ care.
Christie’s father Michael Harnett, who founded the Rebuild Trust campaign group, said the government had “gone silent”.
“We cannot wait for another tragedy before this inquiry actually begins.”