There is not a "snowball's chance in hell" that the UK will eradicate child poverty by 2020, a government adviser has said.
It is time to "come clean" and publicly admit the target will be missed, according to Alan Milburn.
The former Labour health secretary, who now advises ministers on social mobility and improving youngsters' life chances, said an extra £19 billion will be needed to meet the milestone.
Mr Milburn is the government's choice to become chairman of the new Social Mobility and Child Poverty Commission.
At a pre-appointment hearing this morning, he told the Commons Education Select Committee that on current trends, the earliest child poverty will be eradicated is 2027.
"The only way we're going to hit the 2020 target is if one or other political party commits to what I don't think any of them are going to do."
This would be to "bring about a bigger redistribution of income than we have ever seen at any time in our country", he told the cross-party group of MPs.
It is also about "whether or not a political party is prepared to commit £19 billion worth of additional expenditure to realising the 2020 target", he added.
"I think there is a moment for honesty here. I think it is time for all the political parties to either put up or shut up.
"I don't believe, frankly, that there is a snowball's chance in hell that we will hit the 2020 target.
"I think that's very widely privately acknowledged and I think it should be publicly acknowledged too. It is time to come clean about this stuff."
Mr Milburn said he believed there were great intentions and a focus in parts of government on dealing with child poverty.
But he added that these are not "auspicious times" for making progress on the issue.
Under the last government, child poverty did fall, he said, but not "far enough or fast enough".
"Those were far sunnier times," he said.
"We now face two considerable headwinds. The first headwind is the state of the economy and the second headwind is what's happening with public expenditure.
"When you have a situation where the economy is stagnating, public spending is flatlining, inequality is probably widening - these are tough times.
"What would be wrong in my view is if, in those tough times, it was the poorest people who end up paying the heaviest price.
"I think there is a primary responsibility on government to ensure that is prevented from happening."
Mr Milburn told the committee that what has not been done, under any government, and what needs to be done is to "set out what the plan is to hit the target and by when".
He suggested that it may be necessary to decide what the immediate priorities are, because there is a danger, and concerns among child poverty groups, that by saying the 2020 target will not be hit, it takes the pressure off to meet it.
"For me the priority would be a cohort of kids, who are under five, who are in deep poverty, there are around 800,000 of them right now, I would focus really hard on what you could do for them, and a big part of that would be early years education."
That would require "political muscle" and the engagement of the prime minister as well as Secretaries of State, Mr Milburn said.