The families of two workers killed in a 2008 tower crane collapse on East 91st Street say they are furious that they and the public are being locked out of “substantive” pre-trial discussions as the case moves toward a February manslaughter trial.

Manhattan Supreme Court Justice Daniel Conviser – newly appointed to preside over the trial of accused killer crane magnate James Frank Lomma – has repeatedly conducted business in the case in off-the-record conference phone calls to the parties, the families complain in a letter to a Manhattan administrative judge.

“We believe that these telephone conferences are addressing substantive matters off the record and for all intents and purposes “behind closed doors,” reads the letter to Manhattan Supreme Court Justice Michael Obus, and signed by Susan Karten, lawyer for the family of Ramadan Kurtaj, and Bernadette Panzella, lawyer for the family of Donald Christopher Leo.

“These are highly unusual telephone conferences — and they’re not solely for the purpose of scheduling, but are touching on very substantive matters involving new evidence in the case,” said Karten.

It was not known what action, if any, Obus would take regarding the families’ Dec. 6 letter. Lomma, head of New York Crane, has not been in court since Nov. 3, and is not scheduled to return until his trial date, now set at Feb. 21.