Since the 2015 general election, the Labour party has gained around 300,000 new members – most joining after Jeremy Corbyn was elected leader. Momentum, the movement born out of his leadership campaign, has 23,000 members and 200,000 supporters. Compared with the Tories’ meagre 140,000 or so, Labour now has a huge resource of people who can beef up its election campaign on the ground.

But a common criticism of Momentum activists, and Labour’s surge of new members, is that they’re armchair activists. Fairweather supporters more interested in looking virtuous on social media, and voting in leadership elections, than pounding the pavements.

Indeed, one Momentum insider describes the organisation as a “standing army” – but for campaigning to re-elect Corbyn when the time comes, not for campaigning for the Labour party. Another admits if Labour has simply gained a “passive” new support base, then it’s “pretty useless”.

YouGov’s recent polling of Labour’s members suggests that those doing the bulk of the campaigning are pre-Corbyn members. When asked if they’d delivered leaflets for the Labour party, 30 per cent of pre-Corbyn members said they had, to the 20 per cent of new members who had. The difference was 15 per cent to 8 per cent, when asked if they’d been canvassing or doorknocking, 6 per cent to 3 per cent on phonebanking, and 33 per cent to 20 per cent on attending local Labour party meetings.

When interpreting this polling, former Labour MP James Plaskitt argued that, “it looks as if the Corbyn supporters are mostly ‘armchair’ activists”. He added:

“The question for Labour has to be, how long will the grassroots activists stick it out under a leadership they mostly dislike? The polling shows that 50 per cent of this group have considered quitting the party in the last 12 months. If they do start to walk away, there are few new grassroots activists to take up the hard slog of the ground campaign.”

“It is unfair to call them armchair generals”

But this polling was from a small sample, and taken before the snap election was called. And since campaigning began, it looks like this image could be changing. Momentum has launched an online tool called My Nearest Marginal to help its members and supporters go out doorknocking for Labour in their nearest marginal seat. It provides a car pool service so that participants can get to the campaign spots easily and cheaply to target marginal seats. All they need to do is type their postcode in, and the map shows where it is most useful for them to go.

Momentum did this on a smaller scale for Labour campaigning in the Copeland and Stoke-on-Trent Central by-elections. This puts it ahead of the Labour party, which provides no such service specifically for marginal seats – though you can type your postcode in and find the nearest campaigning event to you on its website.

“Momentum is using innovative technology to mobilise thousands of people in marginal seats”

The organisation also has a few volunteers on board from the Bernie Sanders campaign. They are holding training sessions for people in doorknocking and other forms of campaigning, and have also helped Momentum set up peer-to-peer texting, which was used by Sanders activists to help supporters text each other about nearby events and canvasses.

Adam Klug, Momentum National Organiser, commented:

“Momentum is using innovative technology to mobilise thousands of people in marginal seats campaigning for a Labour government. My Nearest Marginal makes it as easy as possible for people to find the swing seat near them where they can have the most impact, and to carpool there with other activists, delivering Labour’s message about building a Britain for the many, not the few.”

According to the organisation, over 100,000 calls have been made on their phone canvassing app so far, and they’ve already run 16 campaign days (involving doorknocking) in marginal constituencies (including Croydon, Crewe & Nantwich, Plymouth, and Hampstead & Kilburn – where 150 people turned out). It aims to run 50 such sessions ahead of polling day.

“Activism has not ticked up in the way you would expect given the massive growth of membership”

Although Momentum is using technology that hasn’t existed in British election campaigning before, the impact of Labour’s surge of new supporters has yet to be felt on the doorstep throughout the country. I’ve spoken to a number of sources working on campaigns in different types of constituencies, and hear mixed reviews.

A source in a highly marginal Labour-held seat where membership has doubled since Corbyn’s election has seen the new supporters coming out doorknocking, and say it’s “unfair” to characterise them as “armchair generals”.

But they do note that turnout has not been proportional to the huge increase in Labour’s support base. “The activism has not ticked up in the way that you would expect given the massive growth of membership,” they tell me. “The idea was we’ve got all these new activists and this is going to make a substantial difference to the ground game – it’s not. But it would be unfair to say that none of them are coming to anything – some have turned up.”

I hear from a marginal London campaign that Momentum activists are turning out for them and that their relationship with the local party is good. The numbers are “not huge”, but their presence is appreciated.

Others have been less impressed. An official at a London CLP in a very safe Labour seat, whose membership has massively increased since Corbyn’s election, notes that their new members have rarely made an appearance at party meetings since they joined.

“None of them are doing anything, literally refusing to come out”

One Labour MP in a safe northern seat tells me they have seen “literally zero door-knocking” from their 250 new members, and I hear a similar response from an insider in a closely-held Labour seat in the north. “There’s all these new members, hundreds of new members, and none of them are doing anything, literally refusing to come out,” they lament.

But the assumption that pro-Corbyn supporters are lazier than others is wrong. Many of those who voted for Corbyn, in both elections, are long-term members of the party – his support came from all types of Labour voters, not just the newbies.

Corbyn’s support base is often characterised as simply young people and students. It’s not – there are lots of baby boomers and professionals who backed him too, as well as older, well-established party members. The latter – with long-term loyalty and time on their side – are more likely to turn out to campaign, whoever the Labour leader, than those with work and education commitments.

In comments that riled the party ahead of the general election in 2015, former Labour minister David Blunkett told me: “There is a question about just how much energy and time we put in to traditional ways of campaigning and how much of a result we get,” warning his party that, “it wouldn’t be a bad idea if Labour reflected on what in the 21st-century actually wins votes, as opposed to reinforcing the vote you already have.”

As the weeks ahead of polling day unfold, it will become clearer how much of an impact Momentum’s new technology will have on Labour’s ground game. But with so much manpower at its disposal, the party will have to come to terms with the limits of on-the-ground campaigning if it doesn’t see a big increase in activity.

Correction: This article initially stated that Labour does not have basic details of campaigning events on its website. It does provide these details here, though you are not directed to your nearest marginal seat.