I'm really not sure if people actually want to debate this, or just criticise Blackpool council's decision tbh, but I'll give it a go.
There is no universally agreed definition of child poverty, but there are some commonly used ones. Under current Department of Work and Pensions criteria, there are a range of measures of child poverty.
In this case, under those DWP definitions, a child is considered to be living in poverty if their household income is less than 60% of average wages, therefore living in "relative low income," when measured against whether the poorest families are keeping pace with the growth of incomes in the economy as a whole - ie in a 'typical household.'
Last year (2011) that 60% threshold figure was £251 per week, which means, at government estimates 2.3 million children were/are living in poverty. The Institute for Fiscal Studies is currently predicting that figure will rise by 300,000 in the lifetime of this parliament.
There are wider and deeper social implications over time for all of us.
http://www.cpag.org.uk/child-poverty-facts-and-figures