Workers on the NHS test-and-trace operation who are being paid £9.50 an hour were charged out to the government’s supplier, Serco, at as much as £21.50 an hour, the Guardian understands. The rate was charged by Sensée, a London-based call centre company, for workers tasked with calling the contacts of people who had tested positive for Covid-19, a source said. Neither Serco nor Sensée disputed the figures. The revelation prompted further concerns about the value for money offered by the test-and-trace system. Led by the Conservative peer Dido Harding, it has already faced scrutiny over efficacy, although the proportion of contacts reached by private-sector contact tracers has improved since earlier in the pandemic when it lagged behind public-sector tracers. Tim Sharp, the TUC’s senior employment rights policy officer, said: “This rate looks excessive and seems to go beyond the already-inflated rates of commission commonplace in the industry. “Instead of just cashing in on the hard work of agency workers, recruitment agencies should treat their workers fairly and pay them properly. Too many agency workers face unpredictable hours, limited rights and low pay.” Serco was limited to earning a margin of 4% on top of costs for its test-and-test work, but its suppliers were not under the same obligation. Sensée did not say how much profit it made on the contract. The full test-and-trace system is budgeted to cost £37bn over two years, or almost £550 for each person in the UK, but the government and its private suppliers have provided few details of how the money was spent. The £1.3bn budget for contact tracing included contracts worth £720m for 2020-21, split between Serco, a member of the FTSE 250 index, and Sitel, a French-owned call centre company. Serco hired as many as 24 employment agencies to find workers for its contact tracing system in the scramble to find the 18,000 workers required by the government. The Guardian has previously revealed that Serco’s supply chain – not including Sensée – was using companies that experts feared could be defrauding the Treasury via a notorious tax scheme. Sources not related to Sensée in other parts of the contact tracing system have reported spending days waiting to make calls. Sensée said its rates were standard in the call centre industry. Both Sensée and Serco highlighted that the overall rate also covers the cost of technology, management, holiday, sickness, and mandatory pensions and national insurance payments. The costs of employing temporary workers through agencies can vary greatly, and the pandemic may have added to costs by making recruitment more difficult. However, Sensée’s website also touts the potential for “cost reduction” for its model – which predated the pandemic – of employing call centre workers from home, eliminating spending on offices and potentially allowing the recruitment of workers from anywhere with an internet connection. Software used by contact tracers was run centrally, by Sitel and Public Health England. RingCentral, a calling technology provider, in October said that many large call centre providers charged their clients rates of below £20 an hour for each worker. A Serco spokesperson said: “Our sub-contractors providing contact centre services will incur a number of costs that are in addition to the wages paid to call handlers.” Mark Walton, Sensée’s chief executive, said: “Our charge rates for outsourced work are competitive within the contact centre industry. If an employer was to employ contact centre advisers themselves, they would incur a wide range of other costs in addition to wages.” A Department of Health and Social Care spokesperson said test and trace “has had a dramatic impact on reducing the spread of the virus”, an opinion at odds with the government’s scientific advisory body, Sage, which found it had only a “marginal impact on transmission”. The government spokesperson said: “The use of third-party suppliers enabled us to quickly respond to the pandemic, especially during the winter peak. Trace handlers and clinical workers across all our partners are paid in line with standard sector rates to ensure all staff are fairly paid for their life saving work.”