Founded in October 2015, the group has been credited with mobilising supporters online and in the streets during the general election campaign earlier this year, which saw the Labour leader perform better than most pundits had predicted.
The group was formed following Corbyn’s victory in the Labour leadership race and has since become highly influential – and controversial – within Labour circles.
Critics of the group claim its activists have taken over constituency Labour parties and agitated against sitting MPs who are critical of the leader.
Momentum said it has added 1,500 new members since Labour’s conference in September and it now has 31,000 activists across 170 local groups, with 15 members of staff.
Co-founder Adam Klug said: “Over the last two years Momentum has become one of the most significant organisations in British politics.
“Our members have breathed life into the Labour Party by getting involved at a local level, running educational events, getting out into the community and supporting workers’ struggles across the country.
“The same can’t be said for the Tories.
“The lifeless, moribund Conservative Party on show in Manchester last week was a good example of what happens when a party doesn’t empower its members. The intellectual energy disappears, a lack of vision sets in and members begin to desert the party.
“Conservatives should be embarrassed they only have 100,000 members and we’re committed to making sure that ordinary people from across the country continue to join Labour and get involved in their local Labour parties.”