The police union has slammed a “dirty trick” by the Australian Federal Police (AFP) amid its enterprise bargaining fight.

Reports say the AFP inserted pop-ups on its internal investigation database that urged users to vote for a new pay deal, which has since failed.  

“Members were horrified that someone saw fit to use the operational system to push this industrial message and it's a blatant misuse of that system,” AFP Association (AFPA) president Angela Smith said.

“Our phones melted down. Emails, texts, Facebook. It just went berserk.”

Ms Smith called it an “unbelievable dirty trick”.

“You cannot use an operational policing system for political propaganda. You just can't do it,” she said.

The union says the offer would have stripped AFP members of pay, leave entitlements and other conditions.

The AFP described its message as “an error of judgement”.

“The item was removed well before there was any contact from the AFPA on the matter,” it said in a statement to the media.

The message appears not to have worked, after over 80 per cent of staff voted against the pay offer this week.

The AFPA will now restart negotiations.