The NT Police, Fire and Emergency Services executive allegedly threatened to open a criminal investigation into NT firefighters writing slogans on their fire trucks that was part of protected workplace action amid stalled talks on a new EBA, the union representing firies has said.

Firefighters at the Darwin station had written slogans with markers on some trucks relating to inadequate staffing levels and other workplace concerns on Wednesday afternoon when they were approached by two senior officers, including a Superintendent, wearing body-worn cameras who allegedly told them a complaint had been filed about criminal damage to the trucks and that if they did not remove the slogans “a criminal investigation” would commence.

However, the union says the firefighters had been granted the right to write slogans on the fire trucks as part of protected industrial action.

“As part of their protected action firies can put messages on the trucks which are removable,” said Unions NT secretary Erina Early.

“Firies wrote messages on the truck about the state of the fire service. They used wipeable, non-permanent pens. NT Fire and Rescue Services did not discuss with the union or firies about protected industrial action, instead the NTPFES used the over stretched resources of police to threaten their own firies to remove the writing or a criminal investigation will be undertaken.

“[Commissioner Jamie] Chalker and NTFRS executive continue to demonstrate they have no respect for our firies.”

A firefighter familiar with the incident told the NT Independent it was a “scare tactic” by the executive.

“They used their scare tactics to try and prevent firefighters from exercising their industrial rights, which the OCPE [Office of the Commissioner of Public Employment] was fully aware of and the PFES HR was also fully aware of,” they said.

“Chalker and [Chief Fire Officer] Mark Spain have acted against the protected actions directly by claiming this was a criminal act, basically threatening firefighters … but our members will not be intimidated by these actions.”

It is the latest incident in a fractious relationship between Police, Fire and Emergency Services and the firies who have been without a new contract for more than 12 months. Police officers are also currently in EBA talks with the Fyles Government, with the offer of a two per cent annual pay rise on the table for both.

Last May, the union representing firefighters called for Mr Chalker to resign over controversial comments he made at a firefighter recruit meeting, in which he allegedly called union members “bullies” and said he would stop them.

For reasons unknown, Mr Chalker told the recruits – who were in their second day of training – that there was a new EBA being negotiated that will not provide any more money for them, that overtime was a privilege and that fire service union members who “carry rank in the fire service” had been bullying and harassing other firefighters.

“Firies have not forgotten that Chalker called them ‘greedy’ and the NTFRS executive did not support their own firefighters,” Ms Early said.

“The conduct displayed this week is a grub act with the sole intention to intimidate and threaten their employees – our firies. What a waste of taxpayers money and abuse of power. When is Chalker and NTFRS executive going to be made accountable for their actions?”

The Police Fire and Emergency Services media unit did not respond to questions about who authorised the threat to firies and who had lodged the complaint about “criminal damage” to the marked-up fire trucks.