The Government's plans to end child poverty are doomed to failure, its adviser on social mobility has warned as new estimates revealed the UK will be home to 3.5 million poor children by 2020.
A report by the Social Mobility and Child Poverty Commission, chaired by former health secretary Alan Milburn, branded the draft strategy for the next three years a "missed opportunity" and insisted it fell far short of what is needed to prevent the numbers rising.
Mr Milburn said it was a "farce" and "particularly lamentable" that ministers had been unable to agree on how to measure poverty after rubbishing existing measures.
"The Government's approach falls far short of what is needed to reduce, let alone end child poverty in our country," added the ex-Labour MP.
"Our new research shows that the gap between the objective of making child poverty history and the reality is becoming ever wider."
He also called on politicians from all parties to work together to combat the issue, adding: "Willing the ends without the means today merely becomes a broken promise tomorrow.
"Across the political spectrum, party leaders now need to come clean about what they plan to do to hit the targets, or what progress they can deliver if they expect to fall short."
In its report, the commission concluded there were some positive things in the strategy, including the extension of childcare support for low-income families and a greater acknowledgement of the problem of working poverty than before.
But it criticised a lack of any clear measures to assess progress and the absence of a detailed plan covering what needs to happen to jobs, wages and benefits to ensure poverty goes down.
It also identified limited action to get other parts of society, such as employers, engaged in tackling poverty and a lack of new action on in-work poverty as fundamental problems.
In addition it accused the Government of ignoring the impact of welfare cuts and of continuing to distance itself from statutory measures in the Child Poverty Act 2010, which senior ministers describe as "discredited", without suggesting any alternatives.
The findings were published as new research carried out on behalf of the commission by Landman Economics revealed the 2020 child poverty targets will be missed by a large margin.
It estimated that even overly optimistic assumptions about parental employment rates and earnings would still leave more than three million children - 21% - in absolute poverty by 2020 - almost five times the number needed to meet the Government's legal obligation to end it.
To achieve the targets within the current council tax and benefits system, it said, would require "implausible" parental employment rates of close to 100%, combined with big increases in working hours of families in working poverty over and above the requirements of Universal Credit.
A spokesman for the Department of Work and Pensions said: " "We remain committed to our goal of ending child poverty by 2020. Our strategy outlines plans to tackle the root causes of poverty, including worklessness, low earnings and educational failure.
"This approach is a better reflection of the reality of child poverty in the UK today and is the only way to achieve lasting change.
"Under this Government there are 300,000 fewer children living in relative income poverty and 100,000 fewer children in workless poor families. We have just seen the largest rise in employment for over 40 years and unemployment is falling. But there is more to do - and we are getting on with that job.
"The commission's own research highlights the weaknesses of the current child poverty measures - calculating poverty by income alone fails to address the issues which hold people back and that's what we're tackling."