There can be no disguising the calamity that last week’s byelection results suggested for the Labour party, no extenuating circumstance that can excuse the performance of an institution that was once a great power. They were a dismal verdict on the state of her majesty’s opposition. Labour’s continuing decline should concern not just Labour supporters but anyone who cares about effective government and the checks and balances provided by decent scrutiny from a functioning opposition. It is difficult to remember a time when the official opposition was so weak in organisation, bereft of ideas, inept at basic politics and at the same time so supremely arrogant in the presumption of its own righteousness. And no amount of puerile blame-shifting by Jeremy Corbyn and his acolytes – it was the fault of Peter Mandelson, fake news, the “establishment” etc – can hide the dire reality of their predicament.

For Corbyn supporters who dismiss what they see as the undue emphasis on winning elections or poll figures, it might be time for them to scrutinise the parlous state of original thinking in Labour. Corbyn speaks in slogans and appears to have no appetite or capacity to engage in new, innovative ways of addressing a range of issues that confront Labour.

It is always tempting to over-extrapolate from byelections, which can throw up atypical swings never to be repeated in a general election. But if anything, byelections tend to underestimate support for the governing party, and over-reward insurgents who provide voters with an opportunity to provide the government with a mid-term kicking. This makes it all the more telling that it was the government who had the most to celebrate on Friday morning.

The byelections provided two different sorts of test for Labour. Copeland, a seat Labour had held since 1983, should have been an easy win. Jeremy Corbyn’s anti-nuclear position unquestionably made things trickier, given the importance of the nuclear energy industry to local jobs. But the byelection took place in the shadow of the threatened closure of a local maternity unit, which Theresa May refused to condemn. There are few local issues more emotive than hospital closures, yet the Conservative candidate was still able to command a 6.7% swing from Labour.

In Stoke, the test was whether Labour could hold back Ukip in a seat that should have proved fertile territory for its leader Paul Nuttall. Labour met this test but its vote share fell and the government’s went up.

Had it not been for a disastrous campaign fought by Nuttall, Labour’s vote might have been eroded further. The Labour campaign failed to inspire disgruntled voters to come out and deliver the sharp verdict on the government one might expect in a safe Labour seat: turnout was below 40%.

As David Miliband argued yesterday, Labour has never looked further from power in the past 50 years. The consequences go far beyond the small increase in Theresa May’s slim Commons majority. If the byelection results swings were replicated across the country, election experts predict Mrs May would win an overall majority of nearly 100.

In normal circumstances, it would be a no-brainer for a prime minister with such a small majority to call a general election. But Mrs May’s slim majority makes little difference in a context where the opposition seems more focused on internal dissent than on landing blows on the government, even when the target is relatively easy. As a result, the dynamic shaping our politics is not a healthy electoral competition between the government and its opposition, but between the prime minister and those to the right of her in her party.

And internal party dynamics too often skew politics away from the interest of the country towards the narrow interests of a particular party faction. On the most important question currently facing Britain – the terms of our exit from the European Union – Mrs May has been pushed towards a hard Brexit by the old Eurosceptic right of her own party, in the complete absence of effective opposition from MPs who oppose this outcome.

Beyond Brexit, May is continuing to ignore warnings of an unprecedented funding crisis in the NHS that is leaving no capacity to undertake the medium-term reform needed to make the health service sustainable. She has presided over cuts to social care funding that mean a quarter fewer older people are getting state support with their care needs. Schools in some areas are facing real-term cuts of up to 17% in their pupil funding in the run up to 2020, while the government is expending political capital on defending its planned expansion of grammar schools, which evidence shows will worsen, not improve, social mobility.

In prisons, a lack of sentencing reform and staff cuts have left prisons dangerously overcrowded and understaffed. The government is cutting funding for back-to-work support for the long-term unemployed, including the disabled, by a staggering three-quarters from March. Reforms to local government funding mean councils in poorer areas have had to cut back local services 10 times as much as in more affluent areas. And Philip Hammond has enthusiastically embraced the Osbornomics of his predecessor, continuing to provide tax cuts for big businesses and more affluent families, while cutting tax credit support for low-income working families and increasing business rates for many high-street small businesses. Labour’s opposition in absentia is clearing the decks for May to firmly pitch herself on Labour’s territory, by claiming the Conservatives are now the party that represents ordinary working people. She is facing little scrutiny over the fact that this rhetoric is undermined by much of what her government is doing.

Labour’s current problems go far beyond its current leader. Labour’s support among the working classes has been in steady decline since 1997. But under Jeremy Corbyn’s leadership, that trend has accelerated: there was a dramatic fall in working-class support in the first two months of his leadership. James Morris, a former Labour pollster, on these pages writes of the disdain working-class voters often express for Mr Corbyn in focus groups.

But the problem goes even beyond ideology: the sheer incompetence of Corbyn’s leadership means Labour is effectively giving up the game of opposition to Conservative backbenchers and the media.

At least there is growing dissent being expressed by the unions, the party’s most significant source of funding. The GMB has now been joined by the likes of Dave Prentis at Unison. But the key powerbroker, Len McCluskey at Unite, remains supportive. His moderate challenger, Gerard Coyne, in Unite’s current general secretary elections, is rightly asking tough questions about why a large chunk of member subs has been used to prop up a failing Corbyn leadership.

For now at least, most of the power in the political system lies firmly in Mrs May’s hands. Labour’s prospects of winning the 2020 general election look forlorn, leaving Britain facing the prospect of 15 years of austerity compounded by a hard Brexit. In choosing to cling on, Jeremy Corbyn – and those whose support is keeping in him in place – can answer to that.