The Office of the Children’s Commissioner for England has ruled that Boris Johnson made misleading claims about supposedly falling child poverty levels at prime minister’s questions, but backed claims made by Keir Starmer. Researchers for the commissioner, Anne Longfield, concluded that Johnson was wrong to claim that there were 400,000 fewer families living in poverty now than there were in 2010 and that it was “generally false” for him to say overall poverty levels were falling. In contrast, the fact-checking report by her office found that Starmer, the Labour leader, was correct to say 600,000 more children now lived in relative poverty compared with 2012, and the total number of children in poverty was forecast to rise steeply. The conclusions are something of a humiliation for the prime minister, who had followed a series of underwhelming PMQs performances against Starmer with a more bullish approach last week, which cheered some Conservative MPs. After Starmer had asked Johnson about a report by another government body, the Social Mobility Commission, which found child poverty was rising, the prime minister disputed this, saying there were 400,000 fewer families in poverty than in 2010. The children’s commissioner’s report noted that while there was no source for what Johnson meant by this, government data suggested an extra 800,000 people in families lived in relative poverty in 2018-19 compared with 2010-11. Under government statistics, relative poverty is defined as below 60% of the median net household income in that particular year. Another definition, for absolute poverty, does not vary, and is set as below 60% of the median net household income in 2010-11. The verdict on this claim read: “False. While there is no exact reference for this claim, it is not consistent with the official statistics.” Johnson also claimed at PMQs that “absolute poverty and relative poverty have both declined under this government”, something the report said risked being “not specific enough to be verified”. However, it concluded the claim was “generally false”, as there were no government statistics showing declines in both measures. There had been a handful of years where one of the gauges fell, but it would be “a very selective reading of the data” if Johnson relied on this for his claim. In contrast, the researchers said official statistics did back up Starmer’s claims that 600,000 more children live in relative poverty compared with 2012, and said it was credible to cite a claim that the total number of children in poverty was projected to rise to 5.2 million by 2022. The latter figure comes from the Social Mobility Commission report, which in turn cites calculations by the Institute for Fiscal Studies thinktank. The researcher said: “It remains to be seen whether this forecast will materialise, and the forecast is now out of date because of Covid-19. But this caveat is not sufficient to disprove the claim: if there is reason to believe that Covid-19 will worsen poverty rates – in which case the claim is actually optimistic.” Longfield, whose role it is to stand up for the interests of children, commissioned the research from her staff after she was asked about the PMQs clash by ITV’s Robert Peston on his podcast last week.