Ten-minute slots for GP appointments could be hampering the number of patients diagnosed with dementia, experts have said.
Researchers said that clinicians have difficulty properly assessing patients with memory problems in just 10 minutes.
Meanwhile complex criteria which need to be met before a family doctor can refer a patient to a memory clinic - where formal diagnoses of dementia are made - can also impact the number of patients who receive a diagnosis, they added.
A new paper, published in the Journal of the Royal Society of Medicine, states that Government drives to improve diagnosis rates have led to an increase in the number of patients who are diagnosed with dementia - which is thought to affect 850,000 people in the UK.
In 2015, 62% of those living with dementia had a formal diagnosis, the authors said.
But this is falling short of the Government target to diagnose 75% of the population living with the condition by 2017.
GPs are responsible for referring patients to memory clinics where they can receive a formal diagnosis and get help with their condition.
But the paper suggests that there is considerable variation in referral criteria, with requirements set by some memory clinics that exceed national guidelines.
Lead author Dr Benedict Hayhoe, from Imperial College London, said: "GPs have difficulty assessing patients with memory problems in strict accordance with guidance within a 10-minute consultation.
"In our experience a significant proportion of available consultation time can be taken up by carrying out just one of the brief cognitive tests."
He added: "A system that discourages or delays referral for dementia is highly counterproductive.
"An urgent review of this area is necessary to establish a system that effectively supports patients and clinicians in early diagnosis, treatment and prevention."
He added that it may also be appropriate to allow people with memory concerns direct access to memory clinics.
Commenting on the paper, Dr Matthew Norton, director of policy at Alzheimer's Research UK, said: "It's absolutely crucial that people with dementia should be able to get a timely diagnosis without delay.
"A diagnosis not only helps people to make sense of the symptoms they are experiencing, it opens the door for them to access existing treatments and support to help manage their condition.
"Many people with dementia tell us they struggled to get a diagnosis, and although there has been a welcome increase in the diagnosis rate, we should continue to seek improvements in the way a diagnosis is made."
George McNamara, head of policy at the Alzheimer's Society, added: "While there has been a notable improvement in diagnosis rates, there are still a third of people with dementia who are left in the dark without a formal diagnosis.
"The condition can be incredibly complex to diagnose, potentially requiring multiple tests and assessments - it would be rare for a diagnosis to be made in one 10-minute visit to the GP.
"The health system must to be able to respond to this complexity and anything that could cause delays to someone receiving a diagnosis needs to be urgently reviewed."