Ms Long said: “Alliance will always stand firm in delivering for the people of Northern Ireland.

“Those responsible for this sinister attack on party Headquarters were deliberately trying to incite fear and intimidation. But we will remind them that these reckless acts will never deter Alliance.  

“The abhorrent incidents that we've seen in recent months directed at politicians and political parties have been utterly unacceptable and are a direct consequence of the harmful rhetoric being spread by individuals both in the chamber and on social media.

“This serves as yet another reminder that everyone in public life must play their part in reducing the temperature of the current toxic rhetoric and demonisation. It has a real-life impact and isn’t conducive to stability or people’s safety.

“I would like to thank the police for their prompt and professional response, as well as their ongoing efforts to investigate the incident.”