Offering routine HIV tests to people when they register with a new GP surgeries in high risk areas is cost effective and could save lives, a study has shown.
The researchers are calling for HIV screening to be rolled out to all 74 local authorities in England with high rates of infection by the virus.
High HIV prevalence is defined as having more than two diagnosed infections per 1,000 adults in a given area.
An estimated 13,500 people in the UK do not know they carry the virus that causes Aids, meaning they miss out on treatment and pose an infection risk to others.
Dr Werner Leber, from Queen Mary University of London, who led the study involving more than 86,000 people from 40 GP surgeries, said: "We've shown that HIV screening in UK primary care is cost effective and potentially cost saving, which is contrary to widespread belief.
"This is an important finding given today's austerity. Financial pressures, particularly within local authority's public health budgets, mean that the costs of HIV testing are under intense scrutiny, and in some areas investment in testing has fallen."
The scientists conducted a trial which tested the effectiveness of rapid fingerprick HIV testing as part of the standard health check carried out during GP registration.
They found it led to a four-fold increase in the HIV diagnosis rate.
A mathematical model showed primary care HIV screening in high prevalence areas became cost effective after 33 years. But factoring in the higher costs of care for people diagnosed late showed that screening could become cost effective far sooner than this.
The annual cost of rolling out HIV screening to all 74 high prevalence authorities was estimated at £4 million.
Dr Clare Highton, from the City and Hackney Clinical Commissioning Group (CCG) said: "Public health, specialist and CCG commissioners should take note of these important results showing the value for money of screening for HIV in primary care.
"This intervention means that people with HIV are able to live longer and healthier lives and the spread of infection to other people is halted."
The findings appear in The Lancet HIV medical journal.
Dr Michael Brady, medical director the HIV/Aids charity Terrence Higgins Trust, said the research is "important" and shows the approach is cost-effective and possibly cost-saving.
"Undiagnosed HIV infection puts individuals at risk of preventable illness and death, disproportionately contributes to onward transmission and is an unnecessary burden of cost to the NHS," he said.
"Effective HIV therapy means people can now expect to live a normal lifespan and won't pass the virus on to anyone else. But testing and early treatment is essential to be able to benefit from this.
"We urgently need new approaches to HIV testing that are delivered at scale and targeted at those at risk.
"Testing in general practice is a key component of this because, whilst people living with undiagnosed HIV are not accessing existing HIV testing services, they do visit their GP and there are many missed opportunities to test."
Dr Brady said the UK's national HIV testing guidance has been recommending testing in general practices in high prevalence areas since 2008, with NICE guidelines also recommending the same.
"This important research demonstrates this approach is cost-effective, and may even be cost-saving," he said.
"I hope that policy-makers, commissioners and healthcare providers act on these findings and invest in HIV testing in primary care.
"We have the tools to end HIV transmission in the UK but we won't achieve that without scaling up testing in general practice and other community settings."