Iain Duncan Smith is to condemn the "fixation" with meeting poverty targets, saying they lead to "perverse" policies.
The Work and Pensions Secretary will insist that the relative measures introduced by Labour are arbitrary.
The comments, in a speech to social research group the Joseph Rowntree Foundation, come as Mr Duncan Smith presses for changes to the definition of poverty.
Rather than being based purely on a family's income relative to the national average, he wants to take into account wider circumstances.
The department is consulting on whether factors such as family breakdown and unemployment should be recognised.
Mr Duncan Smith will say: "It is now widely understood that the current relative income measure by itself is not an accurate picture of child poverty.
"Such a narrow focus can drive perverse decisions, fixated on rotating people across an arbitrary line without asking whether a sustainable difference has been made to the family's life, transforming their outcomes so that they do not slip back below the 'poverty line'."
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