"However you measure it"
I believe that it is important how you measure it.
If you use "relative poverty" and a mean average then in any society with a genuine spread of incomes it will never go away. So Governments can go on a never ending social crusade and pour billions into projects that won't achieve anything (sound familiar?).
It also means that a Government could mercilessly hammer on the bottom 50% of society while rapidly increasing the wealth of the top 50%. The "fight" to end poverty continues, sacrifices are asked and made in the name of the fight and the figures begin to show a slow improvement. But meanwhile the top 50% are laughing all the way to the bank (sound familiar?).
Finally it allows people to dismiss it. You can be "relatively poor" but still reasonably well off in this country. And the right wing press can then spout off about "how can you be poor if you can afford a blackberry?" (sound familiar?) which demeans the whole fight.
You're right there is genuine poverty in this country, but we've got to monitor and measure it better than we do. The first Rowntree survey that really looked into poverty shook up the country and began to dispel the lies that poverty was the fault of the poor and not the fault of low wages (sound familiar?) and that examined peoples needs in a very detailed degree.
That's the sort of thing that we need now. And "relative poverty" just doesn't do that, it's just a pointless political football to be kicked about by the political parties while they do nothing to make a difference.