It is a lonely and unglamorous job, being His Majesty’s official opposition, as Labour knows only too well. There were moments when, out of the spotlight, the party’s spokespeople in parliament heroically defended the public interest on some of the most important issues of the day. One example was during the post-Brexit Fisheries Act, where Labour made a formidable case that history has proved right. The question now is whether Labour will use its landslide majority to fix the extraordinary neglect of our marine environment that it previously lacked the votes for.

Back in 2020, when the fisheries bill was making its way through parliament, Labour’s fisheries spokesperson, Luke Pollard, made the case that the prime objective of the bill should be sustainability: there should be a duty on ministers to take the advice of scientists when allocating fishing opportunities so as to avoid overfishing. He also argued that as the right to fish was a public asset, which ministers conceded during the course of the bill, preference should be given to the part of the fleet which had the highest levels of employment and the lowest environmental impact: the smaller boats, whose activities are limited naturally by the weather.

Labour thought the public interest lay in opportunities being taken away from the “quota barons”, the “slipper skippers”, the supertrawler owners and all those who had acquired a quasi-property right from a free state handout in the late 1990s, when British officials were under pressure to get rampant overfishing by the industrial fleet under control – and underestimated the needs of the inshore fleet.

In debate after debate on the fisheries bill, Labour won the argument but was rolled over by a huge Conservative majority. The result of that defeat is now clear. The inshore fleet is on its knees as a result of the twin evils of lack of access to quota and declining fish populations because of poor management. Since 2016, when the Brexit vote took place, the number of jobs in fishing has fallen by more than a quarter. The vast majority of those were from the inshore fleet, changing the character of coastal communities.

The result in terms of sustainability is that Britain is allowing 54% of quota species – staples such as cod, whiting and monkfish – to be fished above levels advised by scientists this year and has done much the same for each of the four years since the act was passed.

It is hard to exaggerate how bad things are for many species. Take the example of Celtic Sea cod. Over 10 years of negligent overallocation, the population has declined by 90%, just so that fishing boats catching other species with a cod bycatch could continue to fish, as Conservative ministers argued they should. These fish may never come back.

Mackerel is still one of the most plentiful populations in the north-east Atlantic. But it is in reproductive decline and not being fished sustainably, thanks to a lack of a sharing agreement between coastal states. How long before mackerel, too, is gone? Britain goes on giving excessive fishing opportunities to a few vessel owners who make extraordinary profits from wiping out one of our last great national resources.

The countdown to Labour having to decide whether it is going to act on the principles it held in opposition is coming this autumn. Ideology is already in conflict with pitiful reality: Rachel Reeves has said she wants to “reset” relations with the EU and reduce checks on British food exports, but senior Brussels sources have said that in return the EU would be looking to negotiate, among other concessions, greater access to fisheries.

One of the areas where the Conservatives performed well is in the protection of offshore marine protected areas from damaging fishing methods. The Conservatives banned harmful fishing gears on the Dogger Bank, the ecological heart of the North Sea. This was a first for offshore protection anywhere in Europe. The UK committed itself to rolling out similar measures across all its offshore protected areas. Similarly, the UK banned a harmful sand eel fishery in its waters to protect populations of puffins, kittiwakes and other species. This was a notoriously destructive fishery which environmental campaigners had complained about since the 1990s.

In our negotiations with the EU these gains cannot be traded away. The only way for British and EU vessels to get more fish is if stocks are managed sustainably. Arguing between ourselves over a dwindling stock is not a solution, particularly when access to each other’s fishing grounds proved to be the most explosive issue in the whole powder keg of Brexit.