The promise of Thatcherism went like this: make the market king and the individual will be liberated from the dead weight of the state and collectivism, free to thrive through their own efforts. Market forces meant more efficiency, competition would drive down costs, and the proceeds of higher growth could be splashed on services and infrastructure.

Then came the reality: insecurity bred by hire-and-fire low-skill jobs and a lack of affordable housing for millions did not feel like freedom, while privatised utilities offering rip-off prices and poor quality services were a humiliating rebuke to the market fundamentalists. The economic growth of the free market era was substantially weaker and far more unevenly distributed than the demonised age of social democracy: even more so after a crash caused by a privately run banking system.

Britain’s infrastructure – particularly outside London – has been left creaking, completely ill-suited to the needs of a supposedly developed nation. Investment to address the dire state of our public realm is long overdue – and this is how Labour should cast its new commitment to free superfast fibre broadband for all. It’s only one pillar of an attempt to modernise a nation whose potential has been held back by a failed market dogma.

“Let us face the future”: this is how Labour’s 1945 manifesto rallied voters in the aftermath of cataclysmic war. There would be “no depressed areas in the New Britain”, it boldly declared, while the nation required “a tremendous overhaul, a great programme of modernisation and re-equipment of its homes, its factories and machinery, its schools, its social services”. It was a vision rewarded with a landslide victory by a nation which, after the vast sacrifices of war, had no appetite to return to the depressed, hungry 1930s.

A Tory election slogan is, 'Unleash Britain’s potential' – but unleash it from what? A decade of Conservative misrule?

Nearly two decades later, Harold Wilson’s Labour promised a “New Britain” which harnessed the “white heat of technology”, using “socialist planning” to “modernise the economy; to change its structure and to develop with all possible speed the advanced technology and the new science-based industries with which our future lies”.

And while Tony Blair’s New Labour offered only modest tinkering – rather than the unapologetically transformative agendas of his predecessors – his party’s rhetoric in 1997, too, was shrouded in the rhetoric of modernity and the future: of delivering a “new Britain”, of “modernising Britain”, of a country “that does not shuffle into the new millennium afraid of the future, but strides into it with confidence”.

These are Labour’s three great victories, all bound together by an audacious claim on the future, even if the substance did not always match the promise. Labour’s new policy on broadband should be notable not because the party is committing to delivering a service for free – but because it represents a return to the tradition of 1945, 1964 and 1997, unleashing the shackles holding the country back from modernisation.

Britain ranks 35 out of 37 nations analysed by the OECD for broadband connectivity, and while 98% of South Korean premises have full-fibre coverage, here the figure is less than 10%. The competition engendered by the market promotes efficiency and cuts costs, we are solemnly told: and yet the costs of competition in broadband amount to £6.2bn because of duplication of effort and resources.

Given that the internet has become the basic infrastructure underpinning our economy and society, one which frames the daily existence of most Britons – everything from work to leisure to claiming social security – here is a tangible example of market fundamentalism that is a drag on progress and economic growth.

A Tory election slogan is, “Unleash Britain’s potential” – but the question is, unleash it from what? A decade of Conservative misrule? A generation of failed market dogma? Labour’s manifesto – unveiled in the coming days – should have a promise of modernisation at its very core. It is time to repudiate the misguided austerity that has constrained the country’s true potential.

One of the difficulties with some of Labour’s existing election promises – a huge investment in infrastructure – is while the sums committed are vast, what the policies mean in practice seems abstract. To make them tangible, the party needs to spell out what they mean for each local community: for transport links, housing, schools, hospitals.

The thread running through it all – just like every successful Labour campaign of the past – should be a claim on a bold, exhilarating new future, made possible by abandoning the manacles holding the country back. That’s how Labour triumphed in the past: it remains the party’s great hope in overcoming the electoral mountain confronting it in 2019, too.

• Owen Jones is a Guardian columnist