Queensland police have dropped charges laid against outgoing Brisbane councillor Jonathan Sriranganathan during a protest outside an international weapons expo last year.

It marks the third time police have backed away from prosecuting the Greens’ Gabba ward representative, in a move that he suggested showed a consistent police pattern of targeting him and criminalising activists.

Sriranganathan, who will hand his council seat to successor Trina Massey next week, will speak publicly about the matter on Wednesday after police abandoned a court date set down for Monday.

Police arrested Sriranganathan in early October after they alleged he refused to obey their orders outside the Land Forces expo in South Brisbane as part of regular protests against the event. He was then given a strict bail condition, which was dropped within weeks.

The two charges – trespass and obstructing police – are now said to also have been dropped due to a lack of evidence, after lawyers for the councillor spent significant time preparing his defence.

“Police have demonstrated a consistent pattern of unlawfully arresting me and targeting me, which reflects a broader trend of police abusing their powers to suppress peaceful protest and criminalise activists,” Sriranganathan said in a statement.

He said he thought officers’ “heavy-handed” treatment of him compared to white politicians who attended protests was partly due to racism, and suggested he may have lasted longer as a councillor if not for this.

Sriranganathan said he had now been “wrongfully arrested” twice, called on Police Minister Mark Ryan to publicly apologise, and questioned the point of protesters following laws if police arrested them anyway.