Labour MP Frank Field – brought in to look at welfare and benefits by the Conservative/Liberal Democrat government – is calling for child benefits to end when youngsters are aged 13 or 14.
The MP for Birkenhead said: "At that age mothers feel even more engaged with work than they are with children.
"They feel more secure with their children when they are over 13 and so on. If you have a crisis at work and can't be home, it's not such a disaster as when you have a seven-year-old coming home from school."
However yesterday, Labour leadership front-runner David Miliband suggested Mr Field was working with the government to "pave the way" to drop the target of eradicating child poverty by 2020.
He said: "The commitment to abolishing child poverty was one of Labour's most visionary moments.
"I was proud to be part of it when I worked on policy for Tony Blair. It is a difficult target for government; but that is the whole point. Our society should be judged by how many children are poor.
"The 60 per cent target is the internationally recognised measure of poverty".
The proposal for a more targeted child benefits system has also raised concerns with charities. A Barnado's spokeswoman said: "We would be concerned if child benefit was stopped for older children. Nearly four million children are living in poverty in the UK today.
"Taxing child benefit and ensuring that any surplus is redistributed to the children and families most in need would unarguably be a step in the right direction".
It is not the first time that Mr Field has disagreed with his party.
In 1997 he was employed as a minister for welfare reform by Tony Blair with the instruction to "think the unthinkable", but quickly lost his job.