The party's ruling National Executive Committee (NEC) on Tuesday (July 12) suspended all constituency meetings during the leadership contest.
When their branch meeting scheduled for Wednesday (July 13) was cancelled with just four hours notice, some 40 Corbyn backers instead headed to the Coach and Horses pub in Isleworth for an unofficial get-together.
There they unanimously passed a motion, which had been on the agenda for the official constituency meeting, calling on Labour members to unite behind their under-pressure leader.
Ban on meetings 'deeply undemocratic'
"This branch supports Jeremy's continuation as our democratically elected leader, and urges MPs to stop undermining him, and start attacking the Tories," the motion read.
Labour member Salman Shaheen, who was at the pub, branded the NEC's decision to suspend meetings "deeply undemocratic".
He said members wanted to show their support for Mr Corbyn but were not attacking local MP Ruth Cadbury , who was among 172 MPs to back a vote of no confidence against him.
"We want to reiterate our confidence in Jeremy and the principled values he stands for. We see him as our next prime minister," said Mr Shaheen.
"He will lead us towards achieving a fairer, kinder, more equal society."
Ms Cadbury has said that she is opposing Mr Corbyn's re-election as she does not believe he is a "prime minister in waiting".
Jeremy Corbyn supporters were this week forced to cancel a planned rally in Ealing as the hall was fully booked.
Mr Corbyn's shadow chancellor John McDonnell MP came under fire for calling Labour "plotters" "f***ing useless".