A stunned passerby filmed the officers confronting 63-year-old Judah Adunbi – who works to smooth relations between police and the black community – and ask for his name.
But when the indignant grandfather refuses and tries to enter his home officers shout "Taser" and shoot the electric gun at his face.
Mr Adunbi, one of the founders of the Independent Advisory Group set up by the police with the ethnic community in Bristol, then falls to the ground.
Police taser their own race relations adviser – after mistaking him for a crook
The way I fell backward on the back of my head. I was just paralysed. I thought that was it. I thought they were taking my life
Embarrassed police chiefs have admitted the local community in Easton, Bristol – and the ethnic community as a whole – would "have concerns" about the incident.
The video shows officers approach Mr Adunbi on the street outside his own home and ask him for his name.
He replies: "I'm not telling you my name. I've done no wrong."
The two police officers followed him to his fate and tasered him to the ground
They then follow him to his gate and taser him to the ground – despite an onlooking neighbour shouting that Mr Adunbi was simply trying to get into his home.
Mr Adunbi, a prominent member of Bristol's black community, said: "At first you don't accuse someone of being someone else. You ask questions.
"The first thing they should have done is come to me in a polite manner. The way they approached me – they were accusing me. That is wrong".
Mr Adunbi thought he was going to die when he was hit by the taser.
An onlooking neighbour shouted that Mr Adunbi was simply trying to get into his home
He said: "I felt that was it because of the way I fell back.
"The way I fell backward on the back of my head. I was just paralysed. I thought that was it. I thought they were taking my life."
He added that he found the situation hard to process after all the years he has dedicated to try and help ease the tensions between the black community and the police.
He said: "It's a little distasteful in my mouth.
Mr Adunbi a prominent member of Bristol's black community
"To know that I'm one of the founder members of the Independent Advisory Group, which was created some years ago in order to improve better relationship between the AfroCaribbean community and the constabulary, and to be treated like this it's difficult."
Both officers involved remain at work and police said they have voluntarily referred the incident to the Independent Police Complaints Commission.
Chief Supt Jon Reilly said: "After reviewing what happened, we voluntarily referred a complaint about this incident to the IPCC.
"Although we don't have to refer an incident in which a taser has been discharged to the IPCC, we want to be as open and transparent as possible.
Mr Adubni says he thought they were taking his life
"I've met Mr Adunbi and we had a constructive conversation. We're aware of concerns within the local community and we take these concerns very seriously.
"I understand the community are going to have concerns. And we'd really like to answer those, but as there's an ongoing investigation that's very difficult for us to do.
"I want to reassure the community the whole incident was captured on body-worn camera. Both officers were wearing it. And we're determined to understand what happened.
"We work really hard to work positively with all communities and I see no reason why that should change".
An IPCC spokesman said: "We are independently investigating a complaint about an incident in Easton on 14 January where a man was Tasered.
"The IPCC investigation follows a referral from Avon and Somerset Police and is in its early stages."