Conservative candidate Lee Anderson has been caught setting up a friendly encounter with a pal to impress journalist Michael Crick while on the doorsteps.
The Parliamentary candidate for Ashfield, Nottinghamshire, momentarily forgot he was wearing the microphone when he set off in between filming to make a phone call.
However, with the cameras still rolling, the sound - and the full phone call - were picked up by broadcasters.
Some have described it as "more Thick Of It than the actual Thick Of it" with others comparing it to Gordon Brown's "bigoted woman" microphone gaffe.
Mr Anderson sparked national controversy over a Facebook video in which he suggested anti-social people should be kept "in tents in the middle of a field picking potatoes or any current seasonable vegetables".
He refused to comment on the anti-social video when campaigning with Mr Crick.
But Mr Anderson, a former miner and ex-Labour Party member, was caught on mic warning his pal he would be knocking on his door.
He then told him to pretend he was not an acquaintance.
"Make out you know who I am the candidate, but not a friend, alright." he is heard to say. "Alright my duck I will see you in a minute."
The man who answered the door to Mr Anderson as Michael Crick watched on was pretending to be an anti-Labour swing voter.
Mr Crick said while there are always suspicions plants are placed during canvassing, this was the first time one had been uncovered in such spectacular fashion.
He said in his MailPlus film: "In all my years filming elections I have long suspected that certain candidates have set up friendly voters to make them look that much more popular.
"But this is the first time we have caught some candidate blatantly in the act."
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The campaigning didn't go well as a woman approached him, separately, and told him: "You jumped before you were pushed."
He accuses her of being "hard left".
"What he's doing is whipping up intolerance in the local community. He's talking about young people, travellers", she added.
Mr Anderson replied: "This is the nastiness of Momentum."
In the video, Mr Anderson asks the journalist to "cut" and says: "There's going to be a s*** storm when this goes out" and "You've just finished my political career".
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