UK military personnel, veterans and their families are being "completely failed" when they need mental health care, a committee of MPs has said.
In a report, they said it was a "scandal" that a "shamefully small" part of the UK's health budget was spent on support for veterans.
The NHS and Ministry of Defence should create a specialist mental health centre those in need, the report said.
The government said it spends millions on armed forces' mental health care.
The recommendations come from the House of Commons Defence Committee - a group of MPs who have been carrying out an inquiry into the issue.
Their report, part two of the inquiry, says that despite improvements, "there is no doubt that some serving personnel, veterans and their families who need mental health care are still being completely failed by the system."
"With specific mental health care provision for armed forces families also non-existent, it is no surprise that many veterans and their families believe that they have been abandoned," the committee added.
It found many servicemen and women often do not seek help because of the stigma around mental health problems and the fear of damaging their career.
And the quality of care given to servicemen and women is a postcode lottery - with "unacceptable variation" across the UK.
'Waiting a year'
Out of an NHS budget of more than £150bn, less than £10m a year (0.007%) was spent on mental health services specifically for veterans, the committee found.
It said demand was "swamping" the capacity with some individuals being forced to wait up to a year for treatment.
The MPs recommended that a "world-class centre for the treatment of mental injuries" should be set up within the next 12 to 18 months, where veterans can go as soon as they are diagnosed.
They suggest it could be located at the Defence and National Rehabilitation Centre at Stanford Hall in Leicestershire. The NHS in England should consult with the MoD to set it up, the MPs said.
And the MoD must also review the help which is available for the families of armed forces personnel and veterans, the report added, as they can also be affected by military life.
Ruth Smeeth MP, who chairs the defence committee, said the MPs acknowledged the work being done by the MoD and UK health departments, "but it is simply nowhere near enough".
She said: "Fundamental issues still clearly exist, with scandalously little funding allocated to veteran-specific services, and it is unacceptable that veterans and their families should feel abandoned by the state as a result.
"It is vital that veterans get the quality of care they need when they need it, no matter where they live, supported by a world-class national centre."
The chair of the British Medical Association council, Dr Chaand Nagpaul, said the situation as it stands was "completely untenable", and welcomed the creation of a specialist mental health facility.
A spokeswoman for the government said NHS England was committed to providing mental health care around the country so anyone can access help as close to home as possible.
"This includes bespoke services for veterans, which have been supported by an extra £10m as part of the NHS long term plan," she said.
"At the same time, the MoD has increased spending on mental health support for those serving in the armed forces to £22m a year, and is working to tackle the stigma around asking for help throughout the military community."