Image copyright Getty Images Image caption John Shaw (centre) has been city manager of Ferguson since 2007

The chief executive of the US city of Ferguson, Missouri has resigned after a federal report alleged widespread racial bias in the city police department and court system.

As Ferguson's city manager, John Shaw, 39, held the legal power to make personnel and policy changes in the police department.

The city council voted unanimously to accept his resignation on Tuesday.

The city's municipal judge has also resigned as a result of the report.

The city came under investigation after a white police officer killed Michael Brown, an unarmed black teenager, in August, sparking weeks of unrest.

A St Louis County grand jury and the US Justice Department found that Officer Darren Wilson acted in self-defence when he shot Brown.

But a US Department of Justice investigation found overwhelming racial bias in the town's policing practices. The report, released last week, detailed how Ferguson officials used the city's police and court system to generate revenue.

Image copyright Getty Images Image caption Ferguson Mayor James Knowles has been the public face of the city government

After Brown's death, Mayor James Knowles has been the public face and voice of Ferguson's city government.

But Mr Knowles is a part-time employee while Mr Shaw ran day-to-day operations of the city full-time.

"I believe that the city of Ferguson has the resolve to overcome the challenges it faces in the coming months and emerge as a stronger community for it," Mr Shaw said in a statement.

The Justice Department report repeatedly cited Mr Shaw's role in encouraging his police force to aggressively ticket motorists as a means to generate revenue.

Mr Shaw said in a statement on Tuesday that his office "never instructed the police department to target African Americans, nor falsify charges to administer fines, nor heap abuses on the backs of the poor".