Plenty of links have been provided to explain what poverty means today. I really don't think it's useful to talk about the 1930's when many families lived in tenements, perhaps sharing one toilet and with no bathing facilities, at considerable risk from TB and other communicable diseases. Do we really want to base our current expectations on those sorts of standards?
Lots of people can refer back to when they were younger - when there was no central heating and indeed very little heating at all, when a holiday was perhaps a rare occurrence and often consisted of a week in the rain in a caravan. But my feeling is that the basics - housing, energy, water and transport - take up a greater percentage of a family's income now than they did then and it invariably takes two salaries to bring up a family rather than one. Most of the older people I know are now living quite comfortably but they are concerned for their children and grandchildren whose futures - particularly with regard to housing, employment and healthcare - are looking increasingly insecure. Some of us can help in providing house deposits, etc., but not everybody can - and none of us can do anything about the increasing decline of middle and low income wages.
There are many individuals and organisations - GPs, nurses, hospital doctors, teachers, social workers, church representatives, charities, etc. etc. - who, based on their own experience and observations, have voiced their considerable concerns about the impoverishment of an increasing number of lower income families. The focus is on children because children are not yet physically and mentally developed and poverty will affect their long term prospects but of course if a child is living in poverty then so are its parents.