A flagship NHS mental health service is failing patients in one in seven areas of England, research by the BBC shows.
People with conditions like depression, anxiety and post-traumatic stress disorder are entitled to psychological therapies, such as counselling.
The NHS is meant to successfully treat half of the people it sees.
But an analysis of official NHS data showed this was not the case in 28 of the 195 local areas of the country in the first six months of this year.
There is a threefold variation in recovery rates between different places, with experts saying if such differences existed in heart bypass surgery there would be an outcry.
Psychologists said some areas were not properly funding services, meaning patients are offered fewer appointments than they really need.
However, NHS England said the programme - called Improving Access to Psychological Therapies (IAPT) - was one of the most ambitious of its kind in the world and had helped hundreds of thousands of people overcome depression and anxiety.
It said despite the problems in some areas, overall IAPT was successfully treating more than half of patients across the whole population.
The findings come as the BBC has re-launched its NHS Tracker, which provides information about the performance of local services, including mental health for the first time.
A tale of two patients
Karla and Imran have both struggled with their mental health. But they have had different experiences in the NHS.
Karla, from Derby, said she got treatment for depression and anxiety quickly and is now in recovery.
She was given a talking therapy, known as cognitive behavioural therapy.
"It has taught me how to express things in healthier ways. Now I don't bottle things up so much.
"It gave me the strength to say, 'you know what, it's going to hurt and it's going to get worse'. Before I didn't talk to anyone. Therapy taught me to accept this is what it is.
"It's given me my life back."
Imran (not his real name) has had a very different experience to Karla, and - six years on from first seeking help for his mental health issues - he is still struggling to access effective ongoing support.
During that time, he has had contact with a wide range of professionals, his GP, social workers and housing support staff - which "didn't amount to anything". He was also referred to a psychiatrist, and later CBT.
None of it has worked for him, and he says it can be hard to negotiate "the system" when you are also dealing with symptoms.
"There's a lot of pressure on you. It's really hard."
You can read more about Karla and Imran's stories here.
How does the therapy service work?
For those with mild to moderate mental health problems, the NHS runs a counselling service called IAPT.
It is available in every part of the country after being launched 10 years ago.
About 550,000 patients suffering from conditions such as depression, anxiety and post-traumatic stress disorder are treated by the service every year.
They are given support ranging from telephone advice from trained therapists to group and one-to-one talking therapies.
Prof David Clark, clinical adviser to NHS England for IAPT and one of the architects of the programme, said it is "widely recognised as the most ambitious programme of talking therapies in the world".
The treatment should help half to recover - defined as no longer being clinically mentally ill by the time they are discharged.
The NHS has struggled to achieve this since the programme was launched in 2008, but improvements have been made and nationally it was achieved last year for the first time. Since then it has almost continuously been hit.
Prof Clark said on others measures, including how long people wait for treatment to start, the service was also achieving its targets proving it was a highly successful scheme.
And he added "most importantly it has helped of hundreds of thousands of people to overcome their depression and anxiety, and better manage their mental health".
But that progress masks the fact some local areas have been struggling.
Figures are published every three months by NHS area. There are 195 areas run by clinical commissioning groups and in 28 of them, fewer than half of patients were successfully treated during both the January to March and April to June periods. Another 27 failed in at least one quarter.
If you look at the April to June period there was a threefold difference between the best and worst.
In Luton, fewer than one in four patients were successfully treated.
In Wirral, part of Merseyside, it was only one in three.
By comparison, more than two-thirds of patients in Stoke were no longer ill by the time they were discharged.
Why do some areas struggle?
Both Luton and Wirral NHS bosses cited high numbers of people on the waiting list as a factor - meaning people have been waiting longer for treatment to start. They both said they had been making progress on this though.
Psychologists say that like many parts of the NHS, services have been squeezed.
They say some areas put more resources than others into the programme - and that means patients are sometimes discharged before they are ready.
Clinical psychologist Dr Ryan Kemp is a director of therapies at Central and North West London NHS Foundation Trust, which runs services across north-west London and in Milton Keynes.
He said that while the NHS should be "proud" of the progress that has been made, he had concerns.
He said in some places the funding was "minimal", which put "pressure to move people out of the service".
Patients who have not recovered may be put on drugs or referred on to services for more complex problems, such as psychiatry, but experts say there are long waits for these services.
Consultant psychologist Dr Mike Scott, who has written and researched extensively about talking therapies, says: "The fact there is such a variation in recovery rates raises questions. If you had this with heart bypass surgery, there would be real suspicions.
"There needs to be an independent assessment."
He believes the true recovery rate may actually be much lower, because the way treatment is assessed is not robust enough.
"I have done research on this and the recovery rate is much more like 15%. The service is provided on the cheap.
"Patients do not get enough sessions."
The 28 areas of the country which did not successfully treat half of patients receiving psychological therapies in the first six months of this year are:
- NHS Blackburn with Darwen
- NHS Bradford City
- NHS Brighton & Hove
- NHS Corby
- NHS Dudley
- NHS East Lancashire
- NHS Fareham & Gosport
- NHS Greater Huddersfield
- NHS Guildford & Waverley
- NHS Harrow
- NHS Havering
- NHS Leicester City
- NHS Luton
- NHS Manchester
- NHS Merton
- NHS Nene
- NHS North East Lincolnshire
- NHS North Hampshire
- NHS Norwich
- NHS Redbridge
- NHS Salford
- NHS Somerset
- NHS South Eastern Hampshire
- NHS South Sefton
- NHS Southwark
- NHS Vale Royal
- NHS Wakefield
- NHS Wirral
Data analysis by Christine Jeavans and Ros Anning