Practices given training and support designed to encourage testing saw a 40% rise in chlamydia cases detected among young people, researchers from Public Health England (PHE) found.
Testing rates more than doubled in the most active practices.
Researchers said the programme should be rolled out across England to boost screening rates.
The study trialled workshops that visited practices to encourage GPs and practice staff to offer opportunistic chlamydia testing more frequently.
Only 16% of tests provided to the national chlamydia screening programme come from general practice. Yet 60% of young people visit their GP each year.
Practice staff say a lack of time, knowledge and confidence about offering the tests has affected how many they provide.
In response, researchers from the Health Protection Agency, now incorporated into PHE, offered practice-based workshops to educate GPs and practice staff on the importance of the tests, the benefits of diagnosis, and how to offer the test to different patients.
It was backed up by computer prompts, posters, invitation cards, practice-specific testing targets and feedback on performance.
More infections detected
A total of 76 practices took part in scheme between April and September 2010, while 81 acted as controls.
However, the practices involved were only informed about the trial after data was collected, so as not to influence behaviour. Prior consent was given by health officials at the local PCTs, and no practices expressed concerns afterwards.
During the time the workshops ran, testing rates in intervention practices rose from 2.43 to 4.34 per 100 registered patients aged 15-24. In control practices, rates increased from 2.61 to 3.0 per 100 patients.
Researchers calculated that workshop practices had a 76% higher test rate than controls during this period. This remained at 57% greater nine months after the intervention ended.
Practices given support detected 2.5 cases per 1,000 patients compared with 2.3 in controls during the intervention - a 40% increase after adjusting for factors such as age and deprivation.
The most engaged practices, which accepted all three offered visits from a support worker, saw an 80% rise in cases detected.
Study lead Dr Cliodna McNulty, head of the Public Health England primary care unit, said: 'General practice is a natural venue to engage young adults in chlamydia testing, and our intervention shows that providing the right skills and resources can significantly improve screening rates in this setting.
'In doing so, we can also create opportunities for young adults to discuss good sexual health in an easily accessible and familiar place.'
The findings have informed a new, broader 3Cs and HIV Programme to improve sexual health services in general practice. Over 70 local authorities covering 500 GP practices have signed up to the scheme so far.
It aims to support practice staff to offer chlamydia screening and information on contraception and condoms to young adults in every consultation, and offer HIV screening to all patients in line with national guidelines.