Armed forces personnel and veterans who need mental health care are being "completely failed by the system" in some cases, according to a report.
The House of Commons Defence Select Committee said it is a "scandal" that in an NHS budget of over £150 billion UK-wide, less than £10 million per annum (0.007%) has been allocated to veteran-specific mental health services.
The committee's report said the NHS should urgently consult with the Ministry of Defence and the Defence and National Rehabilitation Centre in order to establish a world-class centre for the treatment of mental injuries within the next 12-18 months.
The report, called Mental Health and the Armed Forces, Part Two: The Provision of Care, says the committee has welcomed efforts to improve care, but added: "Despite such 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."
The report said: "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 and that the promises made to them in the Armed Forces Covenant have not been kept.
"It is vital that the improvements which the Ministry of Defence, the four UK health departments and the rest of Government are making in this field fully address these gaps and prove to the armed forces communities that, if they have mental health problems, they will be supported.
"Those who have worn the uniform of their country deserve no less."
Committee member Ruth Smeeth MP, said: "We acknowledge the work that the MOD and the UK health departments are doing to improve the mental health care provided to both serving personnel and veterans; but it is simply nowhere near enough.
"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."
She added: "If you can't get access to MOD support then something is going really wrong - we need to fix it.
"What I'm fed up of hearing is 'we're on a pathway, we're on a journey' - we need to fix it and we've called on the Government to fix it within 18 months."
Dr Chaand Nagpaul, BMA council chair, said the situation as it stands is "completely untenable", adding: "It cannot be right that men and women who have put their lives on the line to defend their country are having to wait a year for treatment when they are at their most vulnerable.
"Therefore, we must welcome the proposals for a specialist mental health facility for veterans and service personnel that matches the standards of care that we offer to our physically injured troops."
Lieutenant General (Retired) Sir Andrew Gregory, chairman of military charity SSAFA, told Forces News: "Waiting definitely exacerbates the symptoms and the challenges they face.
"Already their self-esteem may be low and by hanging around, their feeling of worthlessness increases.
"Anything we can do - firstly, to get them to come forward because that is a challenge in itself - quite a lot of them are too proud or don't want to admit they've got problems. Secondly, to deal with them in a timely fashion is really important."
A Government spokeswoman said: "NHS England is committed to providing mental health care around the country so anyone in need of treatment can access help as close to home as possible.
"This includes bespoke services for veterans, which have been supported by an extra £10 million as part of the NHS long term plan.
"At the same time, the MOD has increased spending on mental health support for those serving in the armed forces to £22 million a year, and is working to tackle the stigma around asking for help throughout the military community.
"We welcome the report by the House of Commons Defence Committee and will respond in due course."