At around eight on a Sunday evening, a duty manager somewhere in an NHS trust is working through a list of names on a screen, trying to fill three gaps on a night shift before the ward falls below its safe staffing level. The people she is calling are bank workers, employed on contracts with no guaranteed hours, paid only for the shifts they agree to take, free to say no. That flexibility is not an accident of NHS employment practice. It is the mechanism that keeps wards running when sickness absence spikes, when a post sits vacant for months, or when winter pressure arrives faster than recruitment can respond. It is also, in the eyes of the government's own impact assessment, precisely the arrangement Labour now intends to reform.

The reforms making headlines this week were framed around private employers. Guaranteed-hour offers after a reference period, compensation for shifts cancelled at short notice, and longer notice for rota changes could together cost UK firms close to £2.9bn a year, according to the government's own modelling, with trade bodies for retail and hospitality warning the true figure will run higher once payroll and HR systems are accounted for. The Federation of Small Businesses has accused ministers of a chaotic approach that risks repeating the unemployment pattern of the last government. Retailers and pub groups have been the loudest voices in that argument, and understandably so, given how exposed those sectors are to cancelled shifts and variable demand.

What has had far less attention is that the NHS sits inside exactly the same category of employer. Staff banks exist in almost every trust in the country, covering nursing, healthcare assistants, allied health professionals and increasingly doctors, and they are built on the same zero-hours or as-and-when basis the legislation targets. Guidance already circulating among NHS workforce leaders warns that bank staff who work regular, predictable patterns, which describes a large share of the people covering nights and weekends in pressured specialties, could qualify for guaranteed-hour contracts once the twelve-week reference period comes into force. That would convert what trusts have long treated as flexible, variable cost into something closer to a fixed staffing commitment, at a moment when every trust in England is under instruction to bring its pay bill down.

There is a further complication that makes the NHS case unusually pointed. Analysis of freedom of information data published earlier this year found that the most expensive bank shifts at several major trusts, including some in London, actually cost more than the most expensive agency shifts over the same period. Bank staffing was supposed to be the cheaper, safer alternative to agency reliance, the tool trusts leaned on as they were pushed to cut agency spend. If that assumption is already shakier than policy documents assume, then adding guaranteed-hours obligations and shift-cancellation pay on top does not simply raise costs at the margin. It challenges the basic premise that the bank model is a saving rather than a liability waiting to be recognised.

None of this means the reforms are wrong for NHS staff. Many bank workers cover the same shifts month after month with none of the security a substantive contract would give them, and the case for reform inside the health service is at least as strong as the case made by the TUC for retail and hospitality. But Yvette Cooper now runs a department that will have to absorb this policy as an employer as well as endorse it as a matter of principle, at the same time as John Healey prepares an October Budget already stretched by fiscal rules Burnham has promised to keep. Whether DHSC and NHS England modelled their own exposure with anything like the rigour applied to the private sector is not yet clear from anything published so far. Given how central bank staffing is to how trusts get through a difficult week, that omission is one Whitehall cannot afford to leave unexamined for long.