Residents have had to leave their homes and a number of controlled explosions have been carried out on the object in the Broadlands Garden area.
Stewart Dickson MLA said: “I must condemn those behind this alert, who have succeeded in disrupting the lives of many in a normally quiet area of Carrickfergus.
“My thoughts are with all residents forced from their homes by those intent on dragging Northern Ireland back to the dark days of the past. This action is completely unacceptable and I want to praise everyone who has played a role in ensuring residents were quickly accommodated elsewhere.
“I would ask anyone with information to contact the PSNI as soon as possible.”