The UN children's agency has hailed tremendous progress since the Convention on the Rights of the Child was adopted nearly 25 years ago.

However, Unicef said more than 300 million children are still made to work and over 6m die from preventable causes.

On the plus side, the agency said 90m children who would have died before their fifth birthday if child mortality rates stayed at their 1990 level are alive today.

It credited progress in delivering immunisations, healthcare, water and sanitation.

The UN body also reported a 37 per cent drop in youngsters with stunted growth since 1990 due to improved nutrition and an increase in primary school enrolment, even in the world's poorest countries where only 53 per cent of children gained school admission in 1990 compared to 81 per cent in 2011.

On the minus side, the report on The State of the World's Children 2014 said 6.6m children under the age of five died in 2012, mostly from preventable causes.

It said "a disproportionate number" were from areas cut off from services because of poverty and geography.

Unicef also said 15 per cent of the world's 2.2 billion children are at work, which "compromises their right to protection from economic exploitation and infringes on their right to learn and play."

Also, 11 per cent of girls are married before 15, "jeopardising their rights to health, education and protection."