Now that the two manifestos have launched, we can look at them side by side, and the contrast could not be more stark: Labour’s offer is ambitious and radical; the Tory document is timid and thin. Jeremy Corbyn wants to spark a green industrial revolution to tackle the climate emergency and create a million environmentally friendly jobs; Boris Johnson is hoping to maintain the status quo on everything but Brexit. Perhaps we shouldn’t be surprised by the difference in ambition and scope. The Labour manifesto is the product of a complex, months-long democratic process involving half a million grassroots members. The Tory manifesto comes from the pen of a fracking lobbyist.

While the Labour manifesto technically has one author – Corbyn’s head of policy Andrew Fisher – the document he produces is just one part of a lengthy collaborative process. Each shadow cabinet member, along with their team, has been developing policy according to their particular brief since being appointed. Keir Starmer, Labour’s Brexit spokesperson, is a key example. While forcing the government to release critical Brexit documents and providing essential scrutiny in parliament, the barrister is also widely credited with slowly but surely shifting the Labour position from an unambiguously pro-Brexit stance to one firmly in support of a fresh EU referendum. That push has required detailed policy work. Other frontbenchers, namely Jon Ashworth and Angela Rayner, have dug deep into their own lived experiences to bring out policy solutions close to their hearts, respectively: expanded addiction support services and Sure Start centres in every community.

Labour campaign groups made up of ordinary members have also been formulating their own ideas, and most have enjoyed a high level of access to shadow secretaries of state – especially in the run-up to party conference. It is at this annual summit, held in September, that many of the battles were fought: on Brexit, where “full remain” was avoided but another referendum with remain as an option was agreed; on immigration, which saw delegates overwhelmingly endorse a sweeping set of demands, some of which were strongly opposed by key leadership figures; on the climate crisis, which culminated in a protracted fight in which two sides claimed victory. Remarkable compromises have been made since then – but, crucially, they have been made by everybody involved.

Such a collaborative process, involving so many voices from across the party, is bound to throw up some arguments

If conference delegates – who are elected by local parties, socialist societies and affiliated trade unions – approve a policy motion by a large majority, it goes into the party programme. The “clause V” meeting then picks items from the programme for the final document. This is the final stop on the manifesto-making journey. You might assume that it would be a small gathering of key players – but you’d be wrong. The weekend before last Thursday’s manifesto launch, about 80 people joined to discuss the transformative agenda. Representatives assembled from the frontbench, the parliamentary party, the ruling body, the national policy forum, affiliated trade unions, plus the Scottish and Welsh Labour leaders, and more. They gather in the party’s Southside HQ in London, where electronic devices are handed in and two hours of “reading time” begins. They then go through each section of the manifesto, with the relevant shadow cabinet member fielding questions and suggestions. As one attendee remarked: “It’s a miracle it only took six hours.”

Such a detailed and collaborative process, involving so many voices from across the party, is bound to throw up some arguments. Going into the clause V meeting this year, there were two big contentious issues.

The first, continued freedom of movement after Brexit, has not been guaranteed as requested by conference; instead, it will be “subject to negotiations”. But Labour’s wider offer on immigration has changed in meaningful ways since 2017. The new manifesto says the “no recourse to public funds” policy, which prevents certain migrants from accessing benefits from their local council, should be scrapped. It promises to “review the alternatives to the inhumane conditions of detention centres”, though falls short of closing all detention centres. The biggest change may be the one advocating universal suffrage: a key demand in the conference motion, Labour is now in favour of extending full voting rights to all UK residents. That includes EU and non-EU migrants. The Labour Campaign for Free Movement has reason to be disappointed, as its name suggests, but the activists have been hugely successful in important areas for migrants. Nondiscriminatory national voting rights are rare, and represent an outstanding victory.

The second contentious issue was the extent of Labour’s ambitions in the timing of its mission to decarbonise the British economy. Grassroots group Labour for a Green New Deal (GND) had joined forces with the Fire Brigades Union to push for a bold 2030 decarbonisation target at conference. They were backed by Momentum and the Communication Workers Union. The GND activists wanted the deadline to be for “zero carbon emissions”, to emphasise that the UK should not rely on risky offsetting methods, but they compromised on “net zero” in September. The activist group couldn’t accept anything other than a 2030 date, however, which resulted in two separate motions – one without the date, that was supported by party-affiliated union GMB. Both were approved, and neither took precedence.

Clause V negotiations gave more weight to the concerns of those sceptical about the “just transition”, which claims energy workers will not bear the brunt of decarbonisation. That’s why the manifesto vows to “put the UK on track for a net-zero-carbon energy system within the 2030s – and go faster if credible pathways can be found”, rather than achieve net-zero by 2030. Again, climate activists did not get everything they campaigned for, but they applied pressure that helped produce a heavily climate-focused programme.

Labour’s manifesto: economic experts' verdict on its radical vision Read more

Labour’s manifesto-making process may be messy. It can produce negative headlines, and certainly doesn’t minimise internal conflict. But the difference between the two parties could not be clearer: the Tory offering was written by a lobbyist whose clients include fracking company Caudrilla, gig-economy firm Uber and tech giant Amazon. Labour’s, by contrast, began by bringing together half a million members at a grassroots level – and it has produced one of the party’s most innovative general election programmes ever.

• Sienna Rodgers is editor of LabourList