As many as 33% of children are affected, compared to 30% in England and Scotland, according to Save the Children's The Well-being of Children in the UK study.

Welsh teenagers are also more likely to become single parents or abuse alcohol and drugs.

We still have many children in very low income families and what that can mean is children not having three meals a day

Save the Children

Save the Children is calling on the government to carry out similar studies in the future, to identify what needs to be done to improve the lives of young people in all corners of the UK.

Young people aged 16 and 17 do worse in the educational stakes than their counterparts in other parts of the UK - figures show 8% lack any form of qualifications.

The most badly affected ward in Wales is Tredegar Park in Newport, south east Wales, with 81.7% of children living in poor households.

But those poverty-stricken areas often sit alongside affluent ones, the report found.

In Swansea, the Townhill region has 81.2% of poor children, whereas three miles down in the road in North Killay, only 3% were affected.

Madeleine Tearse, the organisation's UK policy and strategy manager, told BBC News Online: "The UK has the second highest rate of child poverty in Europe... we have got a lot of catching up to do."

Greatest difficulties

In the UK as a whole, Whitfield South in Scotland is the area facing the greatest difficulties overall, with 96.1% of children living below the poverty line.

Almost four million British children live in poverty

In England the local authority of Tower Hamlets is singled out as an area of particular concern, with three out of four children living in families with less than 60% of average income.

Save the Children contrasts the lives of children in these areas with those in Gerrard's Cross, in Buckinghamshire, which has the lowest child poverty rate at 0.5%.

Mrs Tearse said that while child poverty affects 3.8 million young people - down from a high of 4.5 million in the mid-1990s - more still needs to be done.

She said: "We still have many children in very low income families and what that can mean is children not having three meals a day, a warm coat or properly fitting shoes."

Teenage pregnancy

Save the Children said its most striking finding was that while children's lives are generally improving UK-wide, there are increasing disparities between different areas.

We would urge the government to regularly produce its own report on the well-being of children

Jonathan Bradshaw

Northern Ireland, for example, has the highest infant mortality rate, but the lowest teenage pregnancy rate.

Children in Scotland appear to have the worst diets, the highest youth suicide rate but the best overall education attainment.

In Wales, it is the highest rate of teenage pregnancies and the worst alcohol and drugs problems that stand out.

Mrs Tearse said the government needs to take note of its study and carry out further research in the future.