The revelation that a Florida police department was using mugshots of real people for target practice has caused widespread outrage and sparked a protest by clergy on social media.

It was discovered last month that North Miami Beach's police department used pictures of black men at its gun range. National Guard sergeant Valerie Deant was shocked to find one of them in a rubbish bin – with her brother's face on it.

The city council has now banned the practice following protests which included the display of poster-sized photos of Police Chief Scott Dennis riddled with bullet holes. Dennis told the Miami Herald that he felt "very, very badly" about the practice.

"I sincerely apologised for what my department has done," he said. "This was a training program that had been going on long before I was here and when I found out about it, I ceased it."

However, the revelations that the mugshots – all of black men – were used at all has played into allegations that police have been careless toward black lives, following the shooting of Michael Brown in Ferguson and the death of Eric Garner in New York. There have been widespread street protest over the issue.

Then a closed Facebook group for Lutheran clergy shared the idea of sending in their own photos for target practice. The Twitter protest adopted the hasthag 'UseMeInstead' and features a number of ministers in clerical collars.

The Facebook statement said: "Although we acknowledge the need for a police force that is trained in the use of their firearms, we feel that, if pictures of human targets are used for target practice, great care should be taken in not allowing the selection of these targets to allow for the dehumanisation of those most vulnerable to police violence.

"Our faith teaches us that all human life is sacred. And when human life is devalued, Jesus teaches us to put ourselves in the place of those whose humanity is denied, just as he did.

"To the members of the North Miami Beach Police: If you must use pictures of real humans for your target practice, we request that you use ours. We're sending pictures of ourselves, in our clergy uniforms, to use."

While the protests have proved popular, some activists have also drawn criticism because most of those taking part are white, and black clergy have largely chosen not to participate.