Boris Johnson has been reprimanded by the UK's statistics watchdog for repeatedly making inaccurate and misleading claims about the government's record on child poverty.
The Office for Statistics Regulation (OSR) said figures used by the prime minister were incorrect after he claimed a huge fall 400,000 fall in the number of families of children in poverty since 2010.
After being contacted by a coalition of poverty charities the OSR said the figures were incorrect wrote an article explaining how poverty was measured to "bring to the attention of the team that prepares briefing for prime minister's questions".
The prime minister had made the claims in prime minister's questions in parliament on 17 Jun and 24 June and during an interview with the BBC on 1 December last year.
The watchdog was responding to a complaint by the End Child Poverty Coalition that the prime minister had three times used official poverty data “selectively, inaccurately and, ultimately, misleadingly”.
“There is no wrong measure, but there is a wrong way of using the available measures – and that is to pick and choose which statistics to use based on what best suits the argument you happen to be making," the blogpost says.
Anna Feuchtwang, the chair of End Child Poverty, said: "It is deeply insulting to the children and families swept into poverty, when data about them is used selectively and misleadingly at the whim of politicians.
"The simple fact is that by any measures child poverty is rising, but instead of tackling the problem, the government risks obscuring the issue and misinforming the public.”
Labour is calling on the Mr Johnson to "correct the record" and said the prime minister should "come clean" about the government's performance.
Labour's shadow education secretary Kate Green said the prime minister was "unable to tell the truth about the hardship faced by so many families struggling to make ends meet", describing his conduct as "shameful".
"The prime minister must now correct the record, both publicly and in Parliament, and ensure that when he next raises his government's damning record on child poverty, he comes clean about what the stats are saying," she said.
The OSR is the regulatory arm of the UK Statistics Authority.