Parts of London have higher rates of tuberculosis (TB) than countries such as Rwanda, Eritrea and Iraq, according to a report.
The capital recorded more than 2,500 new cases of TB in London last year - about 40% of the UK's total.
The report, issued by the London Assembly, found a third of London boroughs exceed the World Health Organisation's (WHO) "high incidence" threshold with more than 40 cases per 100,000 people.
And some borough wards are recording markedly more - areas of Hounslow, Brent, Harrow, Newham and Ealing have rates of more than 150 incidents per 100,000 people.
WHO figures from 2013 show Iraq has 45 per 100,000 while Rwanda had 69 and Eritrea 92. On a whole the UK had 13 cases per 100,000.
Tuberculosis is an infectious disease caused by bacteria, which is passed on through coughing and sneezing. Most people who get TB have had prolonged exposure to an infected person, the report said.
The report calls for Londoners be educated on the disease and the Greater London Authority to include TB services when dealing with rough sleepers.
Dr Onkar Sahota, chair of the London Assembly Health Committee, called the findings "astounding" and urged London mayor Boris Johnson to act.
Dr Sahota said: "If we don't get a grip on London's TB situation now, the harder and more expensive it will be to tackle in the years to come. With pressures on health budgets, we can't afford to take our eye off the ball.
"The mayor needs to take more accountability for TB control in London. He is uniquely placed to drive forward measures for TB prevention, as well as better access to treatment."
Prisoners, refugees, migrants, people with substance abuse issues and homeless people were found to be most at risk of the disease.
However latest figures released by Public Health England showed a decrease in the number of reported cases of TB in England. A total of 6,520 cases of TB were recorded, down from 7,257 in 2013.
The figures showed the London borough of Newham had the highest TB rates in the country, with 107 cases per 100,000 people.
Globally nine million people fell ill with TB and 1.5 million died from the disease in 2013, according to WHO figures. Aside from HIV/Aids, it is the greatest single infectious agent killer worldwide.
Swaziland, in southern Africa had the highest rate of cases globally, with 1,382 cases per 100,000 people.