Collabro returned to the Simon Cowell talent contest on Saturday - two years after winning its eighth series - as part of a special performance to mark its tenth anniversary.
However, according to The Sun, Richard - on the far left in the above picture - told his bandmates about his bombshell decision to quit just moments after they left the stage.
A source 'close to' the 22-year-old said: "He has been unhappy for a long time and as soon as they ended their performance on Saturday he told them he’s leaving.
“It has not been easy for him. Everyone working with the group could see that some of the boys really made his life difficult."
Richard's relationship with the other members has apparently become so strained over the past few months that they avoid sitting with him, told him he should sing and move less on stage, and even abandoned him during a trip to Japan.
However, a Collabro insider responded to the claims by suggesting that Richard is to blame for the tensions within the band.
"There were differing creative views in the group — four have one view and Richard has another," the mole said. "Richard is not a team player like the others. Collabro have had an incredible two years and are not going to give up now."
The other four members apparently issued Richard with an ultimatum after he published a video of himself performing solo at iconic London jazz club Ronnie Scott's.
At the time of writing, Richard's supposed exit hasn't been officially confirmed, with both sides yet to comment on the story.
Collabro have enjoyed success since their BGT triumph. Their debut album 'Stars' topped the UK charts in 2014, while follow-up 'Act Two' reached number two last year.