A first report from the regional public health observatories today reveals a widening gap in life expectancy between people in rich and poor areas. The finding threatens to upset the government's commitment to reduce health inequalities.

The London health observatory says that a baby boy born in the east end borough of Newham, one of the capital's poorest areas, is now likely to die at 71, almost six years earlier than a boy born in the central borough of Westminster, one of the richest.

For baby boys born in the early 1990s, the life expectancy gap between the poorest and richest boroughs was only five years.

Using a London Underground analogy, the report says: "There are six stops on the Jubilee Line between Westminster and Canning Town. As one travels east, each can be seen as marking a year of shortened lifespan."

Differences in infant mortality are also increasing, according to the report, Mapping Health Inequalities Across London.

Although the London average is similar to that for England and Wales as a whole, the capital has relatively high figures in its inner areas.

A boy born in Hackney, next to Newham, is more than twice as likely to die in the first year of life as a boy born in Bexley, in the south-east suburbs.

The London observatory is one of eight regional organisations set up last year to monitor health inequalities. Although it is the first to report, it predicts that other regions will shortly announce a similar widening of the health gap between rich and poor in their areas.

The report concludes: "Inequalities in life expectancy and infant mortality within London have been increasing throughout the 1990s and therefore, if current trends continue, by 2010 inequalities will be even greater than today."

Bobbie Jacobson, director of the London observatory, says: "Our study dispels the myth that the health of Londoners compares well with the rest of the country.

"It uncovers the wide and often hidden health inequalities between communities living cheek by jowl in the capital."

Westminster ranks 26th in the national life expectancy league table for men and 13th for women. Newham ranks 349th for men and 320th for women, out of 352 authorities in England. Even within boroughs, there are vast differences in average life expectancy according to levels of deprivation.

The infant mortality rate in London compares poorly to that in many other European cities, including Berlin, Madrid and Dublin.

Anna Coote, director of public health for the King's Fund, the inde pendent health thinktank, says the report will make salutary reading for politicians. She says: "Three things are now vital. First we need to see the government commit serious resources to reducing the health gap. Second, the NHS must take more responsibility for the overall health of the community it serves. And third, London-wide action to regenerate deprived areas should be undertaken as a priority by the Greater London Authority."

Sue Atkinson, director of public health for London and health adviser to the mayor, Ken Living stone, says that the report "brings home the need for effective action at all levels".

• Mapping Health Inequalities Across London is available at www.lho.org.uk