Fewer than half of GPs have adequate training in mental health, new figures suggest.
Data obtained under the Freedom of Information Act by the charity Mind shows that only 46% of trainee GPs have undertaken a training placement in a mental health setting.
And once qualified, GPs are under no obligation to have any further training despite the fact an estimated one in three GP appointments is related to mental health, the charity said.
It also raised concerns about training for nurses who work in GP practices, saying a 2014 study found that 42% have had no mental health training at all.
Paul Farmer, chief executive of Mind, said: "For most of us, our local GP practice is the first place we go when we're unwell - whether it's related to our physical or mental health. GPs and practice nurses have an incredibly difficult job to do, under enormous pressure and demands.
"A significant number of patients they come into contact with will have experienced mental health problems, yet many primary care staff tell us they haven't had sufficient training to be able to deal with them. That's why we're urging the Government to ensure structured training is in place for trainee and qualified GPs and practice nurses.
"Providing structured mental health training to primary care staff would help ensure they have the knowledge and confidence to provide quality mental health support to the many patients coming through their doors who are struggling with their mental health.
"Offering more training would help patients get the best outcomes while also alleviating some of the pressure GPs and practice nurses experience on a daily basis."
Professor Maureen Baker, chairwoman of the Royal College of GPs, said: "Mental health is a key component of the RCGP training curriculum that all GP trainees must follow and demonstrate their competence in before they can practise independently as family doctors in the UK.
"We have been making the case for some time that specialist GP training should be extended from three to four years in order to focus more time on mental health and child health, reflecting the changing GP caseload and the increasing number of patients who are presenting with mental health issues.
"We hope that today's call from Mind will help strengthen our case."
A Department of Health spokesman said: "We know it is vital GPs and other health professionals are trained to deal with the needs of people with mental health issues.
"Our mental health taskforce recommended improvements and, working with Health Education England, we are already making progress.
"Since 2012, the number of trainee doctors working in mental health settings during their foundation programme has more than doubled, we have seen the highest-ever fill rate for core psychiatry training and mental health nursing trainee places are growing at a faster rate than any other nursing specialty in the NHS."