Alliance representatives have again insisted they will not be intimidated after a shotgun cartridge was taped to the front of the party's offices in Carrickfergus.
It was discovered wrapped to a lock on the door of MLA Stewart Dickson's office early yesterday. Police have taken it away for examination. The same office was ransacked and set on fire last year
The latest incident comes a week after a hoax device was left outside East Belfast MP Naomi Long's office, and is one of a dozen incidents reported to the PSNI since last December.
Mr Dickson, an East Antrim MLA, said it would not stop Alliance continuing to work and deliver for people in the area.
"There is absolutely no justification for this level of intimidation and there should be no place in our society for those who wish to spread fear and intimidation," he said .
"Those behind this unjustifiable attack do not speak for the majority of residents in East Antrim who want to see a peaceful future for our area and Northern Ireland as a whole.
"Clearly there are those among us who want to drag us back to the dark days of the past and I would appeal to anyone with information to contact the PSNI.
"The perpetrators of these acts are obviously threatened by the non-violent, non-sectarian and progressive message of the Alliance Party.
"This latest attempt to intimidate us only highlights their wish to disrupt the good work of Alliance Party representatives who are working to deliver the shared and better future that everyone in our area deserves."
The party hit out earlier this week after a man convicted of breaking into its offices in Larne was given a suspended sentence.
Charles Mervyn Jamieson was caught breaking into the office armed with an axe and crowbar and told police he "hated" the Alliance Party.
Deputy leader Ms Long said the sentence had "sent out the wrong message".
The party has been the target for repeated attacks since Belfast City Council voted in December 2012 to change from all-year flying of the Union flag to designated days.
Alliance held the balance of power on the council – a position it strengthened in the local government elections in May.
Former Chief Constable Matt Baggott said at the time: "It is an outrage to have democratic parties intimidated and burned out simply because they took a democratic decision."