Labour’s plan to reclaim society’s most disaffected and disadvantaged members makes both moral and economic sense and will, the Prime Minister suggested, be the Government’s defining policy. This will distinguish it forever , he said, from the previous Tory administrations - which simply wrote off the poorest sections of society as irrelevant.

Attempts to tackle social problems in isolation will fail, he argued, because “joined-up problems demand joined-up solutions”. Schools cannot on their own be expected to solve society’s ills. “They need the backing of parents and the community, and they need the help of all the different agencies that work with young people.”

Governments in the past have “tried to slice problems up into separate packages - as if you could fix an estate by just painting the houses rather than tackling the lack of jobs or the level of crime.”

While the thinking behind the unit was welcomed in principle by just about everyone working with disadvantaged groups, the launch was seriously undermined by the escalating row over cuts in single parent benefit proposed by the beleaguered Social Security Secretary, Harriet Harman.

Whether this was just a case of terrible timing, or, as the Tories suggested, the launch of the social exclusion unit was a cynical attempt to distract attention from the rebellion, the Government was universally portrayed by the media as promising national renewal on Monday and snatching money out of the purses of its poorest citizens on Wednesday.

The other serious objection raised to the SEU is that there is no extra money to fund such an ambitious undertaking. The unit will be the Prime Minister’s personal project and will operate as a network of ministers, civil servants and professionals in the areas most affected by social decay. Ministers involved include education standards minister Stephen Byers, Tessa Jowell (health), Geoffrey Robinson (Treasury) and Peter Mandelson, the Minister without Portfolio.

Its recommendations will affect departmental spending reviews.

The Prime Minister chose Stockwell Park school in the London borough of Lambeth for the unit’s formal launch (the idea was first announced by Peter Mandelson back in July), and the subject of the first of a series of “summit” discussions was truancy and exclusion.

Its first task will be to find ways to cut the growing number of exclusions (12,500 last year, a 13 per cent increase on the previous year),and to persuade children and their parents how important it is not to play truant.

“For many,” said Mr Blair, “being out of school is the beginning of a slippery slope to crime, drugs and exploitation by others. ” Two former truants, Nehary Green, 16, and Zoe Jennett, 23, were invited to speak at the launch.

Zoe, who is now a local government administrator, blamed her teachers for failing to engage her interest, as well as mixed-abilit y teaching which, she said, held the brighter pupils back: “I was always interested in learning, that was not the problem; the problem was the school itself.”

On the same day, education minister Estelle Morris announced tough new guidelines on truancy in a consultation document which has been sent to all chief education officers and schools.

Parents could face fines if they take children out of school during term-time, and local authoritie s and schools were urged to intervene before truancy becomes a habit.

“The habits of regular attendance and punctuality... need to be established with children and their parents from the very first day of schooling and reinforced at regular intervals,” says the document.

When parents refuse to co-operate, “the Government expects LEAs to use their legal powers to press vigorously for improvements. LEAs should not be afraid to prosecute. ” Parents who offend repeatedly could be fined #163;1,000.

The Education and Employment Secretary, David Blunkett (who, oddly, is not included in the Social Exclusion Unit’s network of ministers) announced #163;200 million to provide after-school homework clubs for half of all secondaries and a quarter of primaries.

Asked how disaffected children could be persuaded to attend, he said it he would rely on teachers to come up with imaginative ideas that would “turn the youngsters on; we must link them with the world of work”.

Maggie Bentley Ross, the headteacher of Stockwell Park school, said that the clubs would only work if “teachers target individual pupils . . . we can’t just issue blanket invitations and hope the pupils turn up.”