As I’m the director of Progress, I doubt many will be surprised I didn’t get the email inviting to join Momentum, the new “grassroots network” and “social movement” being built from the Jeremy Corbyn campaign.

I won’t pretend to have tweeted #JezWeCan, but the Labour Party has a rich tradition of groups with very different views and backgrounds. Progress was delighted to have the Guardian’s Owen Jones, Compass’s Neal Lawson, Class’s Steve Hart, and Blue Labour’s Maurice Glasman speak at our last conference – none of them exactly heirs to Blair. We can disagree without being disagreeable.

Yet reaction to the launch of Momentum has been sharply divided. For those who strongly support Corbyn, Momentum represents an exciting way to engage people with politics, to do practical good without a parliamentary majority, and put the principles that won Corbyn the leadership into action.

Others don’t understand why Momentum is needed at all. Jon Lansman says with disarming honesty that when the campaign began, “we didn’t expect to win” instead planning to use the leadership campaign “to build a new movement that would campaign for the policies and values Jeremy supported”.

But Jeremy did win the Labour leadership. That surely makes the whole Labour party the “social movement” and “grassroots network” that, in the words of Clive Lewis MP, strives “to bring together progressives campaigning for social, economic and environmental justice”. Isn’t it Labour members – of all shades of opinion – who should be invited to be in “every town, city and village to create a mass movement for real, progressive change”?

What’s more is Momentum, like Movement for Change, really about changing communities and winning elections when it is also explicitly about changing the Labour Party?

This apparent mix of external and internal aims has led to concerns about Momentum that are as much about the past as the present.

The battles of the 1980s were fought by groups like the Campaign for Labour Party Democracy, Rank and File Mobilisation Committee, Labour Representation Committee, Labour Co-ordination Committee, Campaign for Labour Victory, Solidarity, and many more. Those weren’t years of open debate about changing the country. They were years of trench warfare over deseletions, reselections, electoral colleges, manifesto committees and proscriptions.

So when those involved in Momentum speak of a ‘defensive agenda’ and that it will “campaign inside the Labour Party to change it”, some understandably hear echoes of the bad old days. When Momentum says it “will work with everyone who supports Jeremy’s aim of creating a more fair, equal and democratic society” the organisers perhaps think of an open movement along the lines of Obama’s Organising for America. Others might think of Militant and entryism.

I can tell you one thing I’ve learned as director of Progress. Nothing is more infuriating than when people assume the worst of you, simply because you disagree with them politically.

One of the reasons Corbyn won the leadership was his promise of a new kind of politics. It would be a genuine shame if Momentum was regarded as merely a new front for old fights.

So I want to offer those involved in Momentum some hard-won advice. We don’t get it all right – that is for sure – but we’ve learned a lot in the process.

First, be open about who you are, and how you’re governed. Quotes from anonymous ‘spokesmen’ and no names will make people wonder who is behind everything. Promises about ‘democratic structures’ need filling out quickly. Let people know who your chair is, who’s on your board, how they were chosen and how decisions are being made.

Next, be transparent. Progress, Compass, Class and the Fabians all get an A rating from “Who funds you”, for being open about our donors and Progress is registered under with the Electoral Commission as a members association. I am sure the same runs apply. It’d be a good idea for Momentum to aim for the same, as soon as possible.

Finally, be clear and upfront about what you’ll do, and who you’ll work with.

So, for example Progress provides training, mentoring and on occasion supports candidates for internal party elections, but only after getting the agreement of our elected strategy board. We won’t let anyone who isn’t a member of the party influence the Labour Party.

We’ll run campaigns with people from right across the Labour movement where we agree, whether on the Trade Union bill, devolution to local authorities or a reformed, progressive Europe.

What we won’t ever do is try to deselect or remove an MP and we back all Labour candidates, whatever their politics.

It’d be helpful for the whole party to hear similar commitments from Momentum.

The last year has been bruising and exhilarating for many Labour members. Renewing our party requires a little more goodwill, a little less suspicion. So I’ll finish with a funny story.

Three years ago, Michael Meacher attacked Progress for being a ‘private company’ set up by a parliamentary researcher, which ‘publishes no details of any membership’. He asked the NEC to investigate us. It was an unfair criticism and the attack was hurtful, but it is quite amusing now Momentum is being formed as the successor to ‘Jeremy Corbyn Campaign 2015 (Supporters) Limited’, a private company with one member, Jon Lansman, who also happens to be Michael Meacher’s own parliamentary researcher.

Don’t worry, Jon. We won’t be asking the NEC to investigate you. This is the new, kinder politics in action.

Richard Angell is Director of Progress