The Queensland police commissioner, Katarina Carroll, has flagged a crackdown on police use of social media after the discovery of Facebook groups posting sexist, racist and homophobic material.

Guardian Australia has seen posts from multiple Facebook groups whose membership is restricted to police officers.

They include posts by Queensland officers suggesting women lie about domestic violence; posts claiming women are not capable of performing certain tasks; and comments that use homophobic and offensive terms.

On Monday, Carroll sent a circular to all serving officers announcing an internal investigation.

“I have become aware of inappropriate content on external social media pages linked to both current and former QPS members,” she said.

“The content brought to my attention is incredibly concerning, disappointing and definitely does not reflect the values of our organisation or the majority of our people. Due to the nature and content of the posts, I must investigate and take any action appropriate to cease the continued publication of this highly inappropriate and offensive material.

“As QPS members, there is a significant risk when posting information on personal social media platforms that it could be perceived or misconstrued as information from an official source and/or sanctioned by the QPS. We also have obligations to adhere to the code of conduct when using these platforms in a personal capacity.”

Carroll said the posts she had seen included comments about fellow officers and members of parliament which were “deeply concerning, nasty, defamatory, and quite frankly beggars belief”.

It is understood Carroll was prompted to act after seeing comments on one page for Queensland officers, Defend the Blue. Queensland officers also post regularly on other closed Facebook groups with a national police membership.

“There are many of you who are ‘passive’ members of these groups and I would ask you to reconsider your membership as your tacit support gives them a sense of legitimacy,” Carroll said.

“There are numerous instances where unprofessional social media comments have resulted in the suspension or dismissal from employment.

“One notable example relates to a senior member of an Australian law enforcement agency who was stood down and later resigned after using an alias on social media to make coarse and crude comments. This is a reminder to us all about the reputational harm which can be caused to the entire organisation by the actions of some individuals.”

Carroll said police were still revising their social media policy, which will “further highlight the risks” and outline expectations of police.

“We are a great organisation which works hard to maintain and enhance our reputation, unfortunately a small number of people can cause a significant amount of harm that can taint us all,” she said.

The Guardian has previously reported that one officer posted in a group seeking to collate complaints from colleagues about domestic violence legislation and the need to “remove the gender bias”.

In September last year, Guardian Australia approached police about a post by a Mackay-based police officer, who took to Facebook to vent his frustration about Queensland police banning officers from wearing the “thin blue line” patch, which has been linked to far-right groups.

The officer said: “So you can wear a patch celebrating two men having sex but can’t wear the TBL.”

Police have said they would investigate any complaint and are in the process of updating and strengthening their social media policy. A spokesperson said the post was “inappropriate” and did not reflect police values.

Recent controversy about police gender targets has also proved a lightning rod for these private pages, including comments sent to the Guardian by a serving officer, who described them as “seriously problematic”.

They include posts that suggest women and Indigenous people were hired or promoted beyond their capabilities, rather than on merit.

One post says: “I’ve saw (sic) some incompetent females get recruited and promoted to fill quotas that will impact the agency in years to come.”