A Green MP's heat bill puts Britain's workplace law on a warming collision course

On 12 July 2026, Hannah Spencer, the Green MP who took Birmingham Yardley in a byelection earlier this year, will rise in the House of Commons to introduce a private member's bill that would, for the first time in British law, set a statutory maximum temperature for indoor workplaces. The text she is putting down would compel the Health and Safety Executive to consult on a binding upper limit, with enforceable obligations on employers once a ceiling is fixed. It is a short procedural vehicle, but the political weight behind it is heavy, and it lands at the precise moment Britain's climate, its labour market and its small-business lobby are pulling in different directions.

Spencer's argument is not that hot offices are uncomfortable. It is that, in the summers the country is now recording, heat has become an industrial hazard on par with unguarded machinery, and that the absence of a legal ceiling amounts to a quiet subsidy to employers who would otherwise have to retrofit, shade or cool their premises. The framing is familiar from continental Europe, where Germany, Spain and France have all moved in the last decade to anchor maximum workplace temperatures in statute or in binding collective agreements. Britain has, until now, declined to follow.

A ceiling that does not exist

The regulatory gap is the bill's organising fact. The Workplace (Health, Safety and Welfare) Regulations 1992 set a minimum workplace temperature of 16 °C, but contain no equivalent maximum. Guidance from the Health and Safety Executive tells employers that indoor temperatures should be "reasonable," without specifying the threshold above which a workplace becomes unsafe. In practice, this means a warehouse operative in a metal-roofed distribution centre on a 35 °C July afternoon and an office worker in a glass atrium have the same legal protection: whatever their employer decides is reasonable.

The HSE does, separately, advise that workplace temperatures should not normally exceed 30 °C for sedentary work or 27 °C for physically demanding roles, but those figures are advisory rather than enforceable. Union solicitors have long argued the gap is exploitable; employer groups counter that a hard ceiling would expose them to prosecution for events outside their control.

Spencer's bill does not itself pick a number. It instructs ministers to consult and then to set, by regulation, a maximum above which employers must take specified steps: providing water, adjusting work patterns, supplying cooling equipment, and in extremis stopping work. That drafting choice is deliberate. It defers the politically radioactive choice of a figure and lets the bill survive a ten-minute rule vote on Friday by design rather than by accident.

What employers say they cannot afford

The bill's most organised opposition comes from the Federation of Small Businesses and the British Chambers of Commerce, who argue that a statutory ceiling would land on firms least able to respond. Their case is concrete: many small employers occupy buildings they do not own, where retrofit decisions sit with landlords, and where the cost of air conditioning for a 40-person floor can run into five figures before installation. A binding ceiling, in their reading, is a compliance cost dressed up as a workers' right.

There is a counter-narrative from the trade union side, and it carries empirical weight. The Trades Union Congress has, for three consecutive years, reported survey data showing that a majority of workers in physically demanding sectors, including construction, logistics, warehousing and agriculture, have experienced heat-related symptoms at work in the prior twelve months. Heat exposure is not an aesthetic complaint for a bricklayer on a south-facing scaffold or a picker in a non-refrigerated fulfilment centre; it is a documented cause of lost-time incidents and acute kidney injury. A ceiling, on this reading, is not a luxury. It is the minimum that a regulated labour market owes its workers.

The disagreement is, at root, about who pays first: the worker, in lost wages and damaged health, or the employer, in capital expenditure. The bill, as drafted, places the cost on the employer. That is why it is a bill at all, and why it will not become law without a fight.

The climate frame

It is impossible to read the proposal without the climate data sitting underneath it. The Met Office's most recent State of the UK Climate report records that the ten hottest years on record for England have all occurred since 2003, with 2022 the warmest year in the series and summer 2025 the fourth-hottest. A workplace temperature ceiling that might have looked like a precaution in 1992 looks, in 2026, like a forecast. The number of days exceeding 30 °C in central England has roughly doubled since the 1990s, and urban heat-island effects guarantee that warehouses and workshops on the periphery of cities run hotter than the official Met Office station reading.

This is the structural argument the Green Party is making, and it is one that cuts across the usual left-right alignment. The bill reframes heat as an externality: a cost generated by a collective failure to decarbonise and built environment design choices, and dumped on the people least able to negotiate their way out of it. That is the same logic, applied to a different pollutant, as the clean-air legislation that followed the great London smogs. The political question is whether the British state, and British employers, accept the analogy.

What the bill can and cannot do

A private member's bill introduced under the ten-minute rule has, by convention, no government support and almost no chance of clearing the Commons without one. Its function is different. It is a vehicle for a vote that puts every MP on the record, and a scaffold for the campaign that follows. Spencer's office has been explicit that the bill is intended to force a parliamentary debate, not to become law in this session. The serious question is whether ministers choose, as they have in the past with asbestos and silica, to absorb the pressure and bring forward their own regulation rather than let a backbencher set the tempo.

The precedent matters. The last time a private member's bill succeeded in rewriting a corner of health and safety law without government backing, it was on a subject, mesothelioma compensation, where the political cost of opposition was prohibitive. Heat is not yet in that category. It may become so if the summer of 2026 produces another record-breaking run, or if a high-profile workplace death is attributed, in a coroner's findings, to the absence of a ceiling. The bill is, in effect, a probe. Its job is to find out how much pain the present arrangement can absorb before something gives.

What remains genuinely uncertain is whether the Treasury would back a regulation that imposes material costs on small employers without commensurate fiscal support, and whether the Department for Business and Trade would be willing to spend political capital on a measure whose benefits accrue to workers and unions rather than to growth. The sources do not specify either position. The bill will find out on Friday.

This publication covered the bill as a stress test of Britain's regulatory state under climatic pressure, rather than as a partisan climate story; the framing question is who pays for a hazard that is no longer rare.