The Government has set a target of less than 7% of children living in persistent poverty by 2020, Work and Pensions Secretary Iain Duncan Smith said.
Campaigners had called for a more ambitious measure, but Mr Duncan Smith said the under-7% goal was consisted with the other targets in the Child Poverty Act.
The Child Poverty Action Group (CPAG) said the Government's decision will "let a lot of children down".
The target is for persistent child poverty, meaning the proportion of children who have been in relative poverty for three of the past four years.
The less than 7% aim was set despite the majority of responses to the Government's consultation calling for the target to be for a lower proportion.
Alison Garnham, CPAG's chief executive, said: "This is a target that will let a lot of children down. The longer a child lives in poverty, the more damage is done to their well-being and future life chances.
"We hope the 7% will be a starting point from which we can move to a more ambitious target as favoured by two-thirds of respondents to the Government 's consultation."
In a written ministerial statement Mr Duncan Smith said the Government is "committed to ending child poverty by 2020 , transforming the lives of the most vulnerable in our society".
He said the Government recognised that " persistent poverty can be particularly harmful to children's life chances" and promised to put efforts to tackle it "at the centre of policy ambition".
The Government's response to the consultation on the target acknowledged "the majority of respondents did not agree with the proposed target of less than 7% and felt that a lower target would be more consistent with the aim of ending child poverty".
But Mr Duncan Smith said: "W e carefully considered all representations made to us and have decided, on balance, to set the persistent child poverty target at less than 7%.
"This is based on detailed analysis looking at the relationship between relative poverty and persistent poverty historically.
"A target of less than 7% is consistent with the other Act targets, provides the most coherent overall suite of targets and will drive continued efforts to address persistent child poverty."
He added: "We will continue to focus Government action on tackling the damaging effects of persistent poverty, exploring what further steps we can take to reduce it as far and as fast as possible.
"We will also keep the degree of ambition of the target itself under close review.
The under-7% target must be debated and approved by the Commons and the Lords before it can be brought into force.
Mr Duncan Smith has been pushing for changes to the way child poverty is measured but told MPs "we are not yet in a position to put these forward".
Dr Mary Bousted, general secretary of the Association of Teachers and Lecturers (ATL), said: "It doesn't matter how many times the Government tinkers with measures of child poverty, the fact remains that it has pushed more children into poverty, introduced a generation to food banks and taken some children back into the Dickensian era.
"We know that children cannot fulfil their potential and do their best at school when their parents or carers cannot afford to give them breakfast, when they are living in crowded accommodation, and when they miss school because they cannot afford the uniform.
"This Government puts Scrooge to shame."