A rightwing lobby group that does not declare its donors is spearheading a campaign to undermine the spread of the four-day week in the UK. The TaxPayers’ Alliance (TPA) has emerged as a key influence behind ministerial attempts in the last week to try to shut down the first public sector trial of a shorter working week at South Cambridgeshire district council (SCDC). There are signs of a town hall fightback, with shorter hours now poised to be introduced in neighbouring Cambridge city council, and eight other English councils said to be considering testing the approach. Glasgow city council said it was monitoring pilot programmes and described the four-day working week as “an aspirational position”. Dozens of private companies have successfully trialled the working pattern, and councils regard it as a solution to acute recruitment and retention problems that nine out of 10 councils say they face. The levelling up, housing and communities secretary, Michael Gove, told council leaders this week he believed “very strongly” that taxpayers “need to have people working a full five-day week”. The TPA, which claims to be a grassroots organisation and is part of a global alliance of free-market advocacy groups known as the Atlas Network, is running a “Stop the clock off” campaign against the four-day week. Advocates of the working pattern – 100% of the work done in 80% of the time for 100% pay – claim the shorter working week boosts productivity, public health and builds a society “where we work to live, rather than live to work”. But the TPA claims the day off amounts to a free holiday and says that is “simply unacceptable” in the public sector. This week, the Guardian reported that shortened weeks were bleeding into schooling, with teachers reporting many fewer pupils attending on Fridays. The TPA has previously been funded by US-based donors, and others it does not name because “many people do not like to talk about or broadcast their political views”. The former chief executive, Matthew Elliott, went on to run the Vote Leave campaign. The TPA has campaigned against socialism (which it says “destroys freedom”), for the abolition of inheritance tax, and to scrap the BBC licence fee. In the House of Commons in May, the Conservative MP Anthony Browne quoted the TPA’s claim that a four-day week in the public sector could cost £30bn a year in lost time. The prime minister, Rishi Sunak, said he was “disappointed” in the SCDC and urged IT “to reconsider its decision”, saying residents “deserve better”. Last weekend, the local government minister Lee Rowley told SCDC to “end your experiment immediately” and claimed it could be in breach of the council’s legal duties to achieve “best value”. He thanked the TPA for its work on the issue. “Claims that services have improved barely stand up to scrutiny, while savings have been exaggerated at best,” Elliot Keck, the TPA’s head of campaigns, claimed. Joe Ryle, the director of the 4 Day Week campaign, described the TPA’s £30bn claim as a “back of a fag packet” calculation and cited a study by the thinktank Autonomy that put the annual cost at around £9bn, although it also estimates it could create more than 300,000 new jobs. SCDC is refusing to stop its trial among 500 desk-based staff and plans to extend it to refuse collectors. It claims the four-day week has boosted recruitment and retention, cutting a £2m-a-year agency staff bill by close to £300,000. It said performance improved in processing housing benefit claims, emergency housing repairs, tax collection and planning, and asserted the councils’ right to “determine their own employment policies”. On Monday, Cambridge city council voted to trial the four-day week for bin crews it shares with SCDC. It called for the government to “reconsider its position”. James Naish, the leader of Bassetlaw district council in Nottinghamshire, told the Guardian it planned to trial the four-day week to try to tackle recruitment and retention problems that could ultimately prevent the provision of services. “It isn’t for the government to say you must work five days a week because that will ultimately damage councils and damage local services if in fact the rest of the job market is moving in a different direction,” he said. Referring to SCDC, a spokesperson for the Department of Levelling Up, Housing and Communities said: “Pressing ahead with the choice to remove up to a fifth of their capacity would need to be backed by clear evidence.” It said this would be made clear in forthcoming guidance to councils. The UK last year ran the world’s largest six month trial of the shortened week. Of the 61 companies involved, 56 extended the trial, 18 of which made it permanent. Atom Bank, which, with 470 staff, is the UK’s biggest private sector employer operating a four-day week, challenged the government’s claim that shorter hours would mean 20% less work. “I would recommend that any enterprise, whether public or private, follows the data,” Mark Mullen, the chief executive, told the Guardian. “All companies experience wastage and fall-offs in productivity.” He said “productivity gaps” can be reduced through the four-day week, thereby offsetting the costs of the apparent reduction in capacity. Labour’s position is unclear. Lisa Nandy, the shadow secretary of state for levelling up, housing and communities, declined to comment. Under Jeremy Corbyn, the party committed to reduce average weekly full-time hours to 32 within the next decade.