Thousands of ethnic minority women in the world's poorest countries are dying from HIV/Aids, TB, malaria and complications in pregnancy and childbirth, yet their deaths remain hidden because governments and international bodies fail to record their health outcomes.

Many more women's lives remain in peril amid efforts to meet the 2015 deadlines for the UN Millennium Development Goals and beyond them.

And some communities in countries described as middle-income states face the danger of abandonment by international donors in spite of their worsening health plight.

This warning is signalled today as the charity Health Poverty Action launches a new report, hours before the UN starts New York discussions over five days on a new set of goals to replace the Millennium Development Goals after 2015, covering topics including inequality.

Most commentators agree that the goals have failed to address inequalities such as those between ethnic minorities and mainstream populations.

The post-2015 framework for international development plans to "leave no-one behind" and commits to a "data revolution."

To truly leave no-one behind, the indicators set to measure progress in the post-2015 framework must be broken down by ethnic and cultural group.

There is strong evidence that the detailed breakdown of data by particular variables can help improve the design and evaluation of health programmes and policy, support country-level advocacy on health issues and help reveal the root causes of poverty and marginalisation.

A detailed breakdown of health data enables researchers to identify the variations in health outcomes experienced by different socio-economic groups, including ethnic groups.

The data may reveal consistently poor health outcomes for individual ethnic groups, for example, or may show that some groups have advantages in one area but not another.

Adding a variable such as gender into the analysis can reveal the combined effects of gender and ethnicity for particular health outcomes, with the potential to shine a light on the interaction of two forms of social exclusion.

For instance, being both a woman and from an indigenous community might confer a greater health disadvantage than being an indigenous male, or being a woman of a more advantaged ethnic group.

For donors keen to improve the measurement of the impact of their donations, encouraging and supporting the collection of such data must become a priority so that the effectiveness of health interventions can be accurately assessed.

The report states that current methods of data collection, which fail to break down health information by ethnic group, are covering up huge disparities between the health of ethnic minorities and majority populations.

It cites life expectancy at just 52 years among Namibia's semi-nomadic indigenous San people, compared to 79 years for the country's German-speaking population.

Yet surveys published in Namibia provide no information about health outcomes by ethnic group.

The district of Tsumkwe in north-east Namibia has the largest concentration of San people, with crowded living conditions and sleeping without insecticide-treated nets contributing to high levels of HIV/Aids, TB and malaria.

According to Health Poverty Action, a low proportion of San people living with HIV/Aids take antiretroviral drugs.

The uptake of treatment to prevent mother to child transmission lags behind the rest of the country.

Deadly TB strains have spread amid the regular failure of TB sufferers in San communities to complete their treatment, as treatment programmes are not well tailored to nomadic communities who move from place to place.

The charity's report says the measurement of progress towards the Millennium Development Goals by national averages, drawn from whole populations, masks health variations among different ethnic groups within each country, hiding communities at risk.

The evidence we do have shows that for example in Ethiopia, the country as a whole is on target to meet goal four and reduce the child mortality rate by two-thirds, but in regions with high concentrations of pastoralist populations the rate is around 40 per cent higher.

And in Guatemala, meeting goal five to reduce maternal mortality by three-quarters remains elusive, with death rates among indigenous women three times higher than among the non-indigenous population.

Health Poverty Action is calling for:

n Indicators to gauge progress against all the post-2015 development framework goals to be broken down by inequity, including ethnic and cultural groups

n Governments in countries such as Britain to support developing countries, including middle-income countries, to invest in better statistics collection and analysis, so that inequities between groups such as ethnic minorities can be tracked and addressed

n A stand-alone goal on equality in the post-2015 framework, as well as goals to address the root causes of inequality, such as enabling progressive tax regimes and providing free health care for all.

It is nothing less than shameful that the deaths of thousands of the world's most vulnerable women remain hidden and unaddressed through the failure to collect vital information about them.

Many, many more could face the same fate, without decisive moves by Britain, other nations, institutions and non-governmental groups.

We cannot stand back and let avoidable tragedies continue to cut short so many lives.

Sarah Edwards is head of policy and campaigns at Health Poverty Action