The former Department of Environment (DoE) was "asleep at the wheel" over drilling at Woodburn Forest near Carrickfergus, the Assembly has heard.
Green Party leader Steven Agnew criticised the department for granting limited rights to the project by InfraStrata without planning permission.
"It should not take Friends of the Earth to tell the DoE how to do its job or what it has missed," Mr Agnew said. "This should have been examined closely at the time. It should have been stopped at that point.
"We should not be drilling, particularly in a public forest in a water catchment area adjacent to a reservoir, without full environmental scrutiny."
People Before Profit MLA Gerry Carroll said it was "nothing short of a disgrace" that drilling had been given the go-ahead just 300 metres from Woodburn reservoir, which supplies water to homes across Belfast.
The criticism came as new Sinn Fein Infrastructure Minister Chris Hazzard moved to prevent similar drilling operations happening in the future via a motion that was passed by the Assembly.