For all the many televised encounters between party leaders, one huge subject has largely flown under the radar during this underwhelming election campaign. In 2019, at a time when the Brexit crisis had overwhelmed national politics, Channel 4 nevertheless devoted an entire pre-election debate to the climate emergency. Boris Johnson didn’t turn up. But, sensing the mood of the times, as prime minister he was soon committing to a “green industrial revolution”. Climate action was high-profile and it mattered.

Contrast that with last week’s final leaders’ debate between Rishi Sunak and Sir Keir Starmer. None of the questions selected from the audience addressed the environment. Aside from one attempt by Mr Sunak to suggest that Labour’s green plans will lead to higher taxes – feeding into the Conservative party’s wider attack strategy – both leaders focused their energy and political capital elsewhere. It has been much the same throughout the campaign. Economists, industrial leaders and environmental campaigners are united in their desire for more proactive green government. But the politics has become difficult.

Given that depressing backdrop, this newspaper’s interview with the shadow secretary for climate change and net zero, Ed Miliband, is both timely and welcome. As Mr Miliband rightly points out, the next government will preside over the remainder of a make-or-break decade in relation to net zero. Crucial climate targets risk being badly missed without a step‑change in Westminster.

Labour’s pledge to reverse the ban on onshore wind in its first days in office would send the right signal, as does Mr Miliband’s message that “Britain is off track and we intend to change that direction”. He is also right to say that if the country is to play a leading role internationally, the right example needs to be set at home. But after five years during which the green agenda has become a target for the radical right, and a short-term focus on reducing debt has stymied investment, vital arguments need to be restated and won if a course correction is truly to take place.

As Mr Sunak has sought to wage culture wars over net zero, the green transition has been portrayed as an extraneous financial burden, and an unwanted imposition at a time of economic fragility. Yet in reality, as the former UK head of Siemens, Jürgen Maier, has emphasised, massive green investment is a prerequisite of future economic prosperity. As the global economy decarbonises, going green is the starting point of a desperately needed British growth strategy, not a discretionary add-on.

Labour, should it fulfil expectations on Thursday and win the election, needs to rediscover this truth and be full-throated in expressing it. Its defensive response to Mr Sunak’s dividing-line strategy led it to abandon the totemic £28bn-a-year spending pledge. Since then, Sir Keir has mainly focused on other themes. But achieving the highest sustained growth in the G7, the boldest of Labour’s five “missions” for national renewal, will not be accomplished without gamechanging levels of green investment. Securing a fair transition, which delivers good new jobs and provides energy security and cheaper bills to less well-off households, will not be possible without a budget to match the size of the task.

Such arguments have not received the airing they deserved, during a campaign that has neglected the major crisis facing the planet. From 5 July that needs to change. The biggest challenge of our age deserves much better than to be kicked into the long grass.