A New South Wales Greens MP who is suing the state’s police force over a series of racist and sexist Facebook posts made or “liked” by serving officers says her case shows why “police should not be investigating police”.

More than two years after officers from Sydney made or “liked” a series of derogatory posts about Jenny Leong on Facebook, the state MP for Newtown is suing the NSW police force in the Human Rights Commission under section 18C of the Racial Discrimination Act.

In March 2016 Leong was the target of a series of racist and sexist posts made by police officers following a post she made on her public Facebook page criticising the use of drug sniffer dogs.

The posts included comments mocking Leong’s ethnic background, including posts such as “Nawww tank u hunny...2 dolla sucky sucky lub u long time” and labelling a relative a “swamp monkey”.

On Monday Fairfax Media revealed Leong has begun proceedings against police because the force has still not told her what disciplinary action the officers faced as a result of investigations into the conduct.

As part of her complaint, Leong is seeking a commitment by NSW police to provide cultural and racial awareness training to all staff, an apology, compensation and a public statement acknowledging that officers engaged in unlawful and offensive behaviour.

Maurice Blackburn principal lawyer Giri Sivaraman, who is acting for Leong, said the complaint had been lodged in a bid to “seek long-awaited answers” from the police about their response to the incident.

“Jenny’s complaint has been passed back and forth within NSW police since she first lodged this in April 2016, yet she still has not received a substantial response from police as to their findings regarding her complaint and actions taken,” Sivaraman said on Monday.

“The social media posts made about Jenny in March 2016 were roundly condemned for being highly offensive and inappropriate, yet NSW police continue to advise only that their investigation has concluded and management action has been taken – very few substantive details have been provided about what that entails and more broadly what is being done to address concerns about racist and offensive behaviour within the NSW Police Force.”

Leong first reported the matter to the former Police Integrity Commission in April 2016. Following an investigation into 10 officers the PIC referred the matter to the Commonwealth Department of Public Prosecutions, advising of possible criminal charges against two of the officers involved.

But the CDPP declined to take the case on, saying there was “no reasonable prospect of conviction” of either officer.

The matter was then referred back to the NSW Police Force last year for an internal review into the 10 officers.

Last December, Superintendent Michael Fitzgerald from the Kings Cross Local Area Command wrote to Leong “to personally apologise” as the commander of the main two officers involved.

“Significant management action has been taken against those officers and other officers involved in those posts,” Superintendent Fitzgerald said.

But despite the apology Leong said no specifics have been provided to her about the outcome of the investigation and a freedom of information request into the matter came back heavily redacted.

She told the Guardian the handling of the complaint showed that “police should not be investigating police”, and questioned the role of the Law Enforcement Conduct Commission in providing oversight of the police during the internal investigation.

The LECC – which has been dogged by concerns of underfunding by the state government since it began operating in July 2017 – contacted Leong in September last year to say that officials would be in further contact about the matter. Leong says she never heard from them again.

“At some point there needs to be some accountability for what has occurred,” she told the Guardian.

“At every stage I have believed that this can’t be handled internally by police, because I think everyone can agree police should not be investigating police when it comes to issues of police behaviour.

“That’s why I referred it to the PIC in the first place and why I urged them to hand it over to the LECC. It’s why I wanted there to be at least some oversight.

“You can know in theory that the idea of police investigating police is not a good idea but what I have seen and experienced over the last two years demonstrates the real problems with that.

“In the absence of any response from the LECC or any oversight I’ve decided I need to hold the NSW police and the bodies that oversee them to account by taking action … to reassure the community that there will be action taken if police behave in a racist or offensive manner.”