The Tories are terrified of a Labour ‘supermajority’ – but there are reasons for Labour supporters to be wary too

Keir Starmer with supporters in Northampton, 24 June. Photograph: Jacob King/PA

Can a political party win too much power? In many ways, it’s a strange fear to raise about Labour, yet the Conservatives have been doing it for weeks now. For only two periods in Labour’s 124-year history has it had huge parliamentary majorities: from 1945 to 1950 and 1997 to 2005. And even those two governments still faced hostile newspapers, sceptical civil servants, suspicious big business, millions of instinctively rightwing voters in the most prosperous regions and the pro-Tory bias of much of the establishment.

For the Conservatives to warn about the dangerous monopoly power of a Labour “supermajority”, having sought and enjoyed such power much more often themselves, is shameless even by their standards. For many Labour politicians, activists and supporters, meanwhile, the possibility that the party could enter an era of rare dominance next week is – though they dare not say it yet – very exciting. If the polls are right, the 2024 election and the Starmer supremacy that may follow could become legends that Labour lives off for decades.

And yet, however emotionally satisfying and politically promising it may be for some, a giant Labour majority would also bring new tensions and contradictions to our politics, both across society and inside the party itself.

The most obvious contradiction is the likely mismatch between Labour’s share of the vote, which polls at present predict will be about 40%, no more than Jeremy Corbyn achieved in his 2017 election defeat, and the much greater proportion of seats Starmer’s party is likely to win. Such mismatches are a constant feature of our flawed electoral system, but this time the disjunction may be on an almost unprecedented scale, with Labour potentially winning well over 400 seats, roughly two-thirds of the total, and the Tories possibly as few as 53, according to the pollster Savanta. The last time one of the main parties won such a disproportionate victory was the Tory rout of Labour in 1931.

For Starmer’s ultra-pragmatic election strategists, to crush the Tories similarly would be a triumph of what political scientists call “electoral efficiency”: winning extra votes only where they matter, in target seats, and not worrying about shedding some support in your safe seats in the process. Starmer’s adoption of this approach – you could call it his “Hartlepool before Hackney” strategy – looks likely to deliver not just an extraordinary victory but to create the impression afterwards that Labour now represents the whole of Britain, as Starmer often says he wants to, with new Labour MPs in every region and country.

Yet this impression will almost certainly be deceptive. The support of four in 10 voters, from what may well be a low turnout, after a campaign that does not feel as if it has gripped the public, is not really an overwhelming national mandate. For a Starmer government, an awkward gap may quickly open up between the strength of its Commons position, raising expectations that Labour can pass almost any legislation, and the limited resources and political will that the government has to transform the country.

Once the thrill of victory wears off, some Labour MPs may also become restive. The bigger a parliamentary party, the smaller chance MPs have of becoming ministers, or even of feeling sufficiently appreciated by the prime minister for supporting him or her in the Commons. Rebelling against the government feels less risky, moreover, when it has a seemingly impregnable majority. If Labour is in power for the foreseeable future, faced with a shrunken, divided and discredited Conservative party, the discipline that Starmer’s leadership instilled in most of his MPs in more challenging times may begin to break down – as it eventually did during Tony Blair’s long premiership.

Like Blair, Starmer may find that a big majority makes business friendlier towards his party. Donations to Labour are already surging. In the second week of the election campaign, it raised 15 times as much money as the Tories. Labour’s offer to form a “partnership” with business appeals to some corporations, especially if the party looks likely to hold office for an extended time. One reason for the often unstated but enduring anti-Labour bias of many businesses is that to shareholders and chief executives, the party rarely seems a solid prospect. A commanding Labour majority, amid Tory disarray, could change that.

Yet in an age when big business can be as unpopular as politicians, collaboration between Labour and corporations could also come at a political cost. An entrenched Starmer government with powerful allies could quickly be seen as a new establishment, as Blair’s administration was, and establishments often provoke revolts.

For Blair, these ranged from massive marches by rural conservatives to Ken Livingstone’s successful leftwing independent candidacy for mayor of London. Starmer could face an even wider range of threats: from the Greens, Reform UK, the Lib Dems, further leftist independents and perhaps a new, even more populist version of the Conservatives, each targeting parts of a vast but vulnerable archipelago of new Labour constituencies. By definition, parties with unusually big majorities have MPs in places where they don’t normally win and which are hard to defend.

Inheriting a weak economy and stretched public finances, forced to make divisive decisions, a Starmer government may have nowhere to go in popularity terms but downwards. Unease about a Labour one-party state, and the fickleness of modern voters, could hasten that decline. In effect, the supermajority would soon destroy itself.

Such a bleak outcome is not inevitable. After Blair’s 1997 landslide, he won another in 2001, as some of his policies paid off and the Tories struggled to renew themselves – their thinking going in circles, as is the case now. The Tories’ understanding of much of the country weakened, since they no longer represented it in parliament.

The 2003 Iraq war and 2008 financial crisis eventually ended New Labour’s dominance. If Starmer wins power easily, over-confidence could lead him into similar disasters. Big majorities can create hubris.

But let’s not get too ahead of ourselves. If you’re on the left, it’s hard not to see at least some potential in another Labour ascendancy. As well as producing some decent policies, it might finally loosen the assumption that most constricts our politics. A huge Labour win next week, however undeserved in purely democratic terms, however temporary, would make a mockery of the belief that the Tories are Britain’s mightiest political force. That’s why they fear a Starmer supermajority so much.

• Andy Beckett is a Guardian columnist