Gordon Brown once said that child poverty was "a scar on the soul of Britain". Now Unicef, which says the true measure of a nation's standing is how well it treats its children, has produced a report card on 21 of the most industrialised nations of the world which shows that the UK is bottom of the class for child wellbeing.

In what is understood to be the first ever three dimensional study on child welfare - taking in statistics and surveys old and new covering the attitudes and lifestyle of children - Britain was found wanting.

Last year it was revealed that more than 500,000 children in London, some 41 per cent, were living below the poverty line, once housing costs are taken into account.

In the rest of the country the rate is 28 per cent, a figure which has steadily fallen in recent years.

But in the capital both governments and charities have been fighting a losing battle, with little consistent progress being made in the past eight years.

The United Nations report, published today, reveals that the richest countries in the world are conversely some of the poorest when it comes to their treatment of children.

Joining the UK with the worst child welfare record is the US, the world's only superpower and considered to be the beating heart of the world's economy.

Both Britain and the US found themselves in the bottom third of the rankings for five of six areas of child welfare.

The Netherlands heads the table, being ranked in the top 10 in all areas covered by the report. They are followed by Sweden, Denmark, Finland and Spain.

Many social studies experts say the only way to reverse the trend is to solve the root of the problem - public attitudes in Britain to children. Some say the modern way of life leaves little time for children, who are often seen in the rat-race culture as a pest.

London Child Poverty Commission chairwoman Carey Oppenheim said London was a "conundrum".

"London is a world city, thriving and prosperous but its prosperity masks shockingly high rates of child poverty," she said.

"London is a world city, thriving and prosperous - but its prosperity masks shockingly high rates of child poverty.

"Child poverty is very concentrated in inner London, but there are also lots of pockets of child poverty in outer London.

"Poverty comes with very heavy baggage, including poor health, overcrowding, fewer chances at school and temporary housing."

Professor Jonathan Bradshaw, of the department of social policy and social work at the University of York, one of the report's authors, said: "Britain has experienced two decades of very rapid increases in inequality and poverty that it is only just beginning to turn around and those instances of wellbeing are the consequence of neglect of children over that long period.

"I hope that people will take notice of this. There are lessons for government, local authorities and schools from this report; there are lessons for parents; but there are also lessons for all of us about the way we treat children.

"We don't behave terribly well to children in our society. We tend to treat them as a nuisance, as antisocial. We try to control them and we imprison them in large numbers.

"It is important that children's wellbeing is dealt with now because it is not good. Goodness knows what kind of adults they will become."

The report says there is no obvious relationship between levels of child wellbeing and economic strength. The Czech Republic, for example, achieves a higher overall rank than several much wealthier countries, among them France, Austria, the US and the UK.

It was in three spheres - family and peer relationships, child behaviour and social wellbeing - that the UK ranked worst of the 21 in the report.

Unicef's study on relationships, in which the UK was seen as the poor relation, looked at the percentage of children living in single-parent families and with stepfamilies, those eating a main meal with parents more than once a week, those who report that parents spend time just talking to them and those who find their peers are kind and helpful.

While more than 90 per cent of children in Greece and Italy said they lived with both parents, which is seen as a positive factor, in the UK and the US it was just 60%, indicating that there are more family break-ups.

The percentage of young people living in single-parent families is highest in the UK (17%) and the US (21%) than in any country belonging to the Organisation for Economic Co-operation and Development (OECD).

Just 65% of 15-year-olds in the UK ate the main meal of the day with their parents "several times per week". Only the US, New Zealand and Finland rated worse in a table of OECD countries.

A Health Behaviour in School-age Children study carried out by the University of Edinburgh, which was a key component of the Unicef report, showed that when 11, 13 and 15-year-olds in more than 30 countries were asked the question "do you find your peers generally kind and helpful," more than half were able to answer "yes" in every OECD country except the Czech Republic and the UK.

A further study showed that just 56% of children in the UK felt they could talk to their parents about any problems and just 65% said their parents made them feel loved. Nearly one in four was unable to say that their parents were there for them when needed.

In finishing bottom by "a considerable distance" of the Unicef table on behaviours and risks, the report authors examined healthy lifestyles, rates on smoking, drunkenness, cannabis use, teenage sex, use of condoms, teenage fertility and violence.

For 16 of the 17 OECD countries with available data, between 15% and 28% of young people had had sex by the age of 15. In the UK it was a staggering 40%.

The UK was also in the top five for levels of obesity. The US was top. In the majority of OECD countries, fewer than 15% of young people report being drunk on two or more occasions. In the UK it rises to almost one in three.

The percentage of cannabis users varies from fewer than 5% in Greece and Sweden to over 30% in Canada, Spain, Switzerland, the US and UK.

Britain also finished at the foot of the table on social wellbeing, in which analysts looked at health, enjoyment of school and life satisfaction. Overall, around 80% of young people consider their health to be good or excellent in every OECD except the UK.

Britain ranked 18th in terms of material wellbeing, which takes in the percentage of children living in homes with equivalent incomes below 50% of the national median or without an employed adult and those where children have reported low family affluence and few educational resources.

Child poverty remained above the 15% mark in the UK, United States, Ireland, Portugal, Spain and Italy. But the US and the UK moved from the bottom of the table into the top 10 for family affluence, indicating a bigger gap between the richest and the poorest in society.

Even the variations between countries in the proportion of children growing up in lone-parent families do not explain national poverty rates, Unicef said. Sweden, for example, has a higher proportion of its children living in lone-parent families than the US and the UK but a much lower child poverty rate than either.