People with mental health problems are being forced to wait 112 days for treatment through the NHS’s talking therapies programme – despite a supposed six-week maximum wait.

Delays in care facing those with anxiety and depression are so long in some parts of England that they could lead to people taking their own life, a leading expert in mental health has warned.

An Observer analysis of waiting time data from the NHS’s Improving Access to Psychological Therapies (IAPT) programme has revealed a huge postcode lottery in the average time it took people referred by their GP both to be assessed and then to start treatment in 2018-19.

In some places, a first appointment, at which patients are assessed, takes an average of just four days but in others it takes 55. Similarly, the average wait between the first appointment and the second – at which treatment starts – varies between 13 and 112 days.

An NHS-wide target requires clinical commissioning groups (CCGs) to ensure 75% of those referred are seen within six weeks and 95% within 18 weeks. Health service bosses admit privately that, while waiting times are being met nationally, some areas are a long way from delivering, mainly due to shortages of the therapists who provide most of the care.

“Since they were introduced 10 years ago, IAPT services have dramatically increased the numbers of people getting access to mental health support. But services are clearly struggling to cope with demand,” said Paul Farmer, the chief executive of the mental health charity Mind and ex-chair of the government’s taskforce on mental health.

“No one should have to wait three months between their assessment and starting treatment, and how long you wait shouldn’t depend on where you live. Not getting the right support can be life-threatening.”

Paul Farmer chief executive of Mind. Photograph: Graham Turner/The Guardian

Four CCGs manage to provide assessments within four days: Wakefield, Castle Point and Rochford, Basildon and Brentwood, and South East Staffordshire and Seisdon Peninsula. However, the same wait is 55 days in Salford, 51 days in East and North Hertfordshire and 49 days in West Cheshire.

Patients in Eastern Cheshire face the longest average waits to start treatment – 112 days – our analysis found. Delays are almost as long in Barnet in London (95 days), while they are 85, 82 and 81 days respectively in West Essex, Milton Keynes and Bexley, also in the capital.

The IAPT programme, introduced by Labour in 2009, is widely admired for helping with common mental health conditions such as anxiety, depression, panic attacks, post-traumatic stress disorder and obsessive compulsive disorder. NHS England has hailed its success in increasing the numbers referred to it to 1.6 million in 2018-19, although only 1.1 million people started treatment and only 582,556 finished their course of treatment, usually cognitive behavioural therapy.

Dr Tim Rogers, a consultant psychiatrist and clinical director of the digital service Big White Wall, which universities and the Ministry of Defence use to provide mental health support online to students and members of the armed forces, said the growing numbers of people seeking help was a positive trend “but it also creates huge challenges in terms of access to and provision of treatment and support.

“It’s clear from these striking data that the scale of this task facing the country means that innovative solutions, including the use of technology, are the way forward.”

Users of Big White Wall’s digital services are less likely to end up in a crisis, use GP and A&E services less and often recover without needing to access IAPT treatment at all, he added.

A spokesperson for the NHS said: “Nowhere in the world has a more successful programme [than IAPT] for helping people with depression and anxiety. IAPT is seeing 100,000 people every month entering treatment, with nine in 10 starting treatment within six weeks after an initial discussion with a therapist about their condition.

“With more than half of people recovering from their mental illness as a result of NHS talking therapies, it is right that countries including Canada, Australia, the US, Norway and Israel are adopting this model for their own patients.”

In the UK and Ireland, Samaritans can be contacted on 116 123 or email jo@samaritans.org or jo@samaritans.ie. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. In Australia, the crisis support service Lifeline is 13 11 14. Other international helplines can be found at www.befrienders.org