More than half the people diagnosed with HIV in Sutton are diagnosed too late meaning they pose a greater risk of passing it on and have worse outcomes.
Sutton is the worst performing borough in the capital in terms of diagnosing people with HIV within four years of them contracting it.
A scientist analyses an HIV test
A leading HIV charity is calling for candidates in May's local elections to make improving the speed of HIV detections in Sutton a priority - or the borough, which has a low rate of HIV, could risk the rate increasing.
The National AIDS Trust (NAT) has obtained figures from 2012, the most recent available, that show nearly 58 per cent of people who were diagnosed with HIV in Sutton, had carried the disease for four years or more. This is the highest percentage in London and worse than the national average.
According to the NAT late diagnosis of HIV leads to worse health outcomes, a decreased life expectancy and a greater chance of passing the virus on.
People diagnosed late also have an eleven-fold increased risk of death within one year of HIV diagnosis compared to those diagnosed promptly.
Yusef Azad, director of policy and campaigns at NAT, said: "London has from the start of the epidemic been the part of the UK most severely affected by HIV, yet Sutton is still struggling to diagnose people living with the virus on time.
"Reducing the late diagnosis of HIV is a key public health responsibility for local councils and so these elections represent a real opportunity for councillors and political groups in Sutton to tackle HIV in the borough.
"We are urging local candidates in Sutton, if elected, to invest in HIV prevention services, show leadership on diagnosis and fund and commission local HIV support services.
"Disinvestment in diagnosis would seriously harm public health, especially in an area like Sutton, and will cost the council and the NHS in the long term.
"The May 2014 elections will be the first to take place since local authorities regained their responsibility for public health – now councillors and political groups in Sutton can make a lasting difference to the lives of people with HIV, those at a higher risk of contracting the virus and the generations to come."
According to the figures, one person in every 417 in Sutton has HIV which makes it a high prevalence area and above the national average of one in 546.
The NAT is encouraging people to get behind the campaign to raise awareness by tweeting with the hashtags #HIVmatters and #LDNmay2014. To find out more, visit www.nat.org.uk.