Introduction Antibiotic overuse is directly related to antibiotic resistance, and primary care is one of the main reasons for this overuse. This study aims to demonstrate that including experts on infectious diseases (ID) within the antimicrobial stewardship (AMS) programme team in primary care settings achieves higher reductions in overall antibiotic consumption and increases the quality of prescription.Methods and analysis A multicentre, cluster-randomised, blinded clinical trial will be conducted between 2021 and 2023. Six primary care centres will be randomly assigned to an advanced or a standard AMS programme. The advanced AMS programme will consist of a standard AMS programme combined with the possibility that general practitioners (GP) will discuss patients’ therapies with ID experts telephonically during working days and biweekly meetings. The main endpoint will be overall antibiotic consumption, defined as daily defined dose per 1000 inhabitants per day (DHD). Secondary end-points will be: (1) unnecessary antibiotic prescriptions in patients diagnosed with upper respiratory tract or urinary tract infection, (2) adequacy of antibiotic prescription, (3) reattendance to GP or emergency room within 30 days after the initial GP visit and (4) hospital admissions for any reason within 30 days after the GP visit. Two secondary endpoints (unnecessary antibiotic therapy and adequacy of therapy) will be evaluated by blinded investigators.We will select three clusters (centres) per arm (coverage of 147 644 inhabitants) which will allow the rejection of the null hypothesis of equal consumption with a power of 80%, assuming a moderate intracluster correlation of 0.2, an intracluster variance of 4 and a mean difference of 1 DHD. The type I error will be set at 5%.Ethics and dissemination The protocol was reviewed and approved by local ethics committees. The results of this study will be published in peer-reviewed journals and presented at medical conferences.Trial registration number NCT04848883
