A shocking set of racist emails sent by senior Ferguson law enforcement officials depict Barack Obama as a chimpanzee and characterize Michelle Obama as a bare-chested African woman, according to a damning federal investigation into civil rights violations committed by the police force.

Extracts from seven emails sent by Ferguson police supervisors, published in a long-awaited US Justice Department report released on Wednesday, were seized upon by investigators as illustrative of the “unequivocally derogatory, dehumanizing” array of communications obtained in the investigation that were “demonstrative of impermissible bias”.

In one email, sent in April 2011, the president is depicted as a chimpanzee. Another, sent in October 2011, includes a photograph of dancing women, “apparently in Africa”, with the caption “Michelle Obama’s High School Reunion”. The authors of the emails were not made clear by the federal report.

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A June 2011 email describes a man seeking “welfare” for his dogs as they are “mixed in color, unemployed, lazy, can’t speak English and have no frigging clue who their Daddies are.” While another, sent in May 2011 stated: “An African-American woman in New Orleans was admitted into hospital for pregnancy termination. Two weeks later she received a check for $5,000. She phoned the hospital to ask who it from. The hospital said, ‘Crimestoppers.’”

Other emails:

Suggest that Obama would not be president for long with the line “what black man holds a steady job for four years”.

Mock African Americans through speech stereotypes.

Include jokes “based on offensive stereotypes about Muslims”.

A separate Justice Department report, also released on Wednesday, cleared the former Ferguson police officer Darren Wilson in relation to the August killing of the unarmed teenager Michael Brown.

The Justice Department report into the broader behaviour of the Ferguson police notes that the emails come from individuals who are all currently employed Ferguson officials sent from their official emails during work hours, and states that some were sent by police commanders.

Although the report does not name the senders of the extracted emails, a footnote reveals that in 2012, the Ferguson city manager, John Shaw, forwarded an email that “played upon stereotypes of Latinos”. However, the city manager then sent another email “within minutes” apologising for the “inappropriate and offensive” message, after claiming not have to seen its entire contents.

“Our review of documents revealed many additional email communications that exhibited racial or ethnic bias, as well as other forms of bias,” the report states. “Our investigation has not revealed any indication that any officer or court clerk engaged in these communications was ever disciplined.”

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The report notes that investigators were able to review many more emails sent by senior Ferguson police personnel, as their correspondence is backed up on hard drives – whereas patrol officers use a form of email that does not retain messages after they are deleted.

The report continues: “The racial animus and stereotypes expressed by these supervisors suggest that they are unlikely to hold an officer accountable for discriminatory conduct or take any steps to discourage the development or perpetuation of racial stereotypes among officers.”