Jeremy Corbyn’s grassroots movement Momentum is to relaunch this week after months of infighting threatened to cripple it.

The movement, created in October 2015 to capture the enthusiasm of Corbyn’s leadership campaign, has been engulfed in debilitating feuds on a scale not seen on the left since the 1980s. Jon Lansman, one of its founders and a close associate of Corbyn, has made a series of moves to end the factionalism. A new national coordinating group is to meet for the first time on 11 March, in Birmingham, shorn of leftwing groups and individuals judged as hostile to Labour.

Two weeks later, on 25 March, Momentum will hold its first national conference, also in Birmingham, building on the events it held in parallel with Labour’s annual conference in Liverpool in September. As part of its new look, the group is to recruit a national coordinator who will act as its public face. The organisation, which has been dubbed Corbyn’s praetorian guard, has about 22,000 members, each paying £10 a year. It also has a much larger database of supporters. Organisers are expecting about 700 to attend the conference.

As well as channelling the energy of young supporters, and inspiring lapsed party members, Lansman and John McDonnell wanted Momentum to be a pressure group to help them shift Labour to the left. But the group became a magnet for many leftwing groups, and individuals well to the left of either Lansman or McDonnell, such as the Alliance for Workers’ Liberty, a Trotskyist group. The AWL is one of the groups excluded from the new-look Momentum. Sam Tarry, one of the original organisers of Momentum and Corbyn’s director of communications and strategy in last year’s leadership campaign, said: “It has been tense. But I think we have come out the other side.”

Tarry, who is on the new 26-member national co-ordinating group – 12 of whom were elected by the membership, four elected by members who are Labour public office holders, six elected by affiliated organisations, and six representatives from affiliated trade unions –added: “There were some people on the old national committee who wanted to use Momentum to promote their organisations and agendas … It was the last hurrah of the old sectarian left.”

Corbyn first responded to the infighting in an email to Momentum members in December, warning that such internal debate could distract Labour from the goal of winning elections. He initiated a survey of views of Momentum members.

In January, Lansman sent out an email disbanding the faction-riven national committee and publishing a new constitution for Momentum. Previously, anyone could join as long as they had not supported a rival group to Labour.

Tarry said: “All Momentum members will have to be Labour party members by 1 July so sectarian groups that are not able to be involved in Labour also cannot be involved in Momentum.”

Elections to the new national co-ordinating group took place between 30 January and 17 February. Forty-two candidates stood for the 12 members’ places, with 7,559 voting. Lansman is on the new committee as a representative from the Left Futures website and Tarry as a union representative – he is a political officer with the Transport Salaried Staffs’ Association.

One criticism of the committee is that all 26 places were not up for election by the whole membership. Among those critical of the changes is Jackie Walker, who was suspended by Labour and stripped of the post of Momentum vice-chair last year for allegedly bringing the Labour party into disrepute. “Jon Lansman’s changes – that were totally undemocratically brought in – are about centralising power and making it more acceptable to Labour party structures. That’s not what Momentum was about. That’s not what gave it its energy or its growth,” he said.

On the day the national coordinating committee gathers in Birmingham a group calling itself Momentum Grassroots will hold an alternative meeting.

Momentum’s annual conference is to be followed by a series of meetings organised by Take Back Control, an events organisation that grew out of Momentum. The goal is to confront the Brexit divide by bringing together pro and anti supporters in marginal constituencies, beginning in Croydon on 8 April, followed by Tower Hamlets in London, Sunderland, Bradford, Plymouth, Norwich, Hastings, York, Barnsley, and Dagenham. McDonnell, shadow home secretary Diane Abbott, and former shadow cabinet members Clive Lewis and Rachael Maskell are being lined up to speak at the events.

Deborah Hermanns, one of Take Back Control’s organisers, said that after Brexit Labour needs to embed in communities that have been ignored for decades to build long-term support.

“This means running food banks, co-operative childcare centres and cinema clubs. It means sponsoring sports clubs, running pubs and opening spaces for community use. It means putting time and resources into building up cultural institutions and providing community spaces in which new political identities can form,” she said.