By Brian Wheeler
BBC News political reporter
The "socially excluded" have always held a special place in New Labour's philosophy.
Young people are the target of much policy
The idea that Thatcherism created a permanent "underclass" of people, jobless and often homeless, cut off from mainstream society, was a central plank of the party's social policy when it came to power in 1997.
Tackle social exclusion, the thinking went, and everything else would follow. The benefits bill would be cut, the crime rate would fall and the UK would cease to have high rates of teenage pregnancy and drug abuse.
What was needed - what had never been tried before - they said, was a "joined-up", cross-departmental assault on all of the social ills afflicting the underclass.
It is a source of shame to many in the Labour Party that eight years down the line many of these problems remain very much alive and the socially excluded - like the poor - are still with us.
It has not, ministers would argue, been for the want of trying.
Since 1997, there have been dozens of initiatives aimed at regenerating the most deprived areas of country - the "pockets" of high unemployment where social exclusion is practically a way of life.
A social exclusion unit was set up within weeks of Mr Blair taking office, initially in the Cabinet Office and then under the control of Deputy Prime Minister John Prescott, with the aim of getting to the root of the problem.
Towards the end of her ministerial career, Mo Mowlam was put in charge of tackling exclusion - a forerunner of the planned social exclusion minister.
But tussles over funding and the arrival of Mr Blair's "respect agenda", which covers much of the same territory, has led to opposition claims the vulnerable are losing out to Whitehall "turf wars".
In the meantime, the Conservatives - who at one time seemed to pour scorn on the idea of social exclusion - have woken up to the problem.
One of the most frequently quoted statistics in the run up to last year's general election was that a million or so young people are not in education, training or employment.
This was held up by the Tories as a sign Labour had failed in one of its key aims - and that it was time for a new approach.
The fact that Mr Blair has now decided to appoint a Cabinet minister with special responsibility for social exclusion will be seen by critics as a final admission of that failure.
It is also, perhaps, a sign of his impatience that many of the social problems he set out to tackle in 1997 are still there.
Mr Blair clearly thinks it is time for a rethink on the issue of social exclusion.
There is a growing mood on all sides of the debate that civil servants and ministers in Whitehall may not have all the answers and that a centralised approach is not the answer.
Socially excluded people tend to lead complicated and chaotic lives and are not necessarily the easiest people to help with initiatives and task forces.
A report last year by the Social Exclusion Unit on "young people with complex needs" found the way they looked at the world - rather than the amount of money they had or the opportunities available to them - was what really needed to change.
"The way in which young people think and behave is highly relevant to shaping their life chances. Their attitudes and assumptions can either compound their disadvantages or can help to overcome them," it said.
In other words, a homeless teenager with a drug problem is likely to make worse decisions in life than someone from a stable and loving home.
The report argued parents and peers were the most important influence on vulnerable youngsters. What they needed, it concluded, was a "trusted adult" who could help them make the right decisions.
The Conservatives, who are conducting their own review of social policy under former leader Iain Duncan Smith, have seized on the idea of "social entrepreneurs" - influential local volunteers who can act as mentors to troubled youngsters or help older people gain control of their lives.
Gordon Brown - who has largely led Labour's assault on social exclusion - has also spoken warmly about social entrepreneurs and the role of the voluntary sector.
But he has also argued that helping the vulnerable is too important to be left to charities and volunteers alone - the state must have a role.
Whatever the new social exclusion minister's precise duties in Cabinet will be, expect to hear much talk from them of "empowerment" of individuals, localism and decentralisation.