Jeremy Corbyn
Matt Zarb-Cousin said democratic socialists were "no longer welcome" in the party and urged others to defect.
The shadow health secretary insisted he made the comment "in jest".
An attempt to pave the way for Corbyn to stand as a Labour candidate at the next general election was defeated.
Party now has 432,213 members compared to 564,443 in 2017.
The former leader has been criticised for an appearance on Al Mayadeen in which he questioned the decision to send military assistance to Ukraine.
Friends of the former Labour leader want him to establish a new 'power base' for his progressive politics in the capital.
Long-awaited Forde inquiry says the party was unable to operate as an effective opposition due to "deep rooted" divisions.
A Twitter classic.
"We’re starting from scratch, the slate is wiped clean," he says.
A former employee at the pollster claimed the survey showed Jeremy Corbyn had won a TV debate during the 2017 election "by a country mile".