Jeremy Corbyn’s landslide victory in the Labour leadership election was the clearest sign yet that not only is austerity not working, it’s increasingly not popular.

Before Corbyn joined the leadership race on a clear anti-austerity platform that argued for a progressive alternative based on investment rather than cuts, the leadership campaign had swang to the right to such an extent that the acid test seemed to have become whether you were willing to denounce New Labour’s spending as being too high.

The backdrop to this remarkable summer was of course Labour’s defeat at the general election where the dominant media discourse was that the Tories had won a landslide victory and were impregnable.

The Tory Party, which only got 24 per cent of the vote, was implementing a viciously right-wing agenda and seemed to be getting away with it.

The votes for parties standing on a clear anti-austerity message — the Greens and the remarkable SNP result in Scotland — were widely ignored.

As well as votes for parties saying clearly they were against austerity, we saw a historic “End Austerity Now” demonstration in June, which even police figures suggested had 250,000 people join it.

Support for Jeremy was amazing from the moment he declared and took off further when the other three candidates abstained on the Welfare Bill.

Across the labour movement, and across British society, this was a clear demonstration that more and more people were not prepared to adopt or support measures that would increase poverty.

The hundreds of thousands of people who supported Jeremy and the hundreds of thousands of people who have taken part in activities against austerity were also right to oppose the cuts on economic grounds.

George Osborne’s economic agenda is not working even though supporters of austerity have been claiming it is. The latest data show that’s clearly not the case. Industrial production is lower than in May 2010 when the Tories were elected and the current account deficit is also at a record level.

Therefore, Corbynomics is absolutely necessary — there’s no sign we’re getting out of this mess without government investment.

At the Labour Party conference, not only were policies agreed that started to set out a clear, popular alternative to austerity — including public ownership of the railways and the need for government intervention when markets fail in instances such as in Redcar — but also we saw what an excellent shadow chancellor John McDonnell will be in challenging Osborne on the key issues.

Since the conference, Labour’s clear opposition to tax credit cuts has led to a damaging defeat for the government in the House of Lords and a desperate bid by the Tories to speak about anything other than the cost of living crisis that has been affecting millions of Britons over recent years.

But this success isn’t just due to Labour’s progressive stance on a single issue — it’s a reflection of the benefits of having a consistently anti-austerity message based on credible, concrete policies that offer an economic alternative and agenda of hope.

As Ken Livingstone put it in a recent piece for the Huffington Post: “Jeremy Corbyn has only been the leader of the Labour Party for a few weeks but he has already delivered significant change in how politics is conducted and in the direction of travel of the Labour party,” adding that “it would be easy, in the light of the froth and noise of minor controversies, to lose sight of just how profound the change has already been.”

Livingstone is quite right to argue that: “Tory chaos over tax credits did not happen by accident,” but was a reflection of how Labour’s “tactics flowed from the strategy of standing up to the government more clearly.”

We now need to defend Corbyn’s leadership against distorting media attacks and continue to build the People’s Assembly Against Austerity movement — and its Labour branch, the Labour Assembly Against Austerity.

We need to work for the future anti-austerity Labour government we so desperately need. Our Labour Assembly Against Austerity Conference on November 14 will be a vital step in this direction. Join us there.

• The Labour Assembly Against Austerity conference will take place 10am–5pm on Saturday November 14 at the Institute of Education, London WC1H 0AL. A vital event to discuss how Labour can win the argument against austerity and build the anti-cuts movement with John McDonnell MP, Clive Lewis MP, Diane Abbott MP, PCS general secretary Mark Serwotka , CWU general secretary Dave Ward, economist Ann Pettifor, Labour executive committee member Christine Shawcroft plus many more. Register at www.labourassemblyagainstausterity.org.uk