Mental health patients are facing an "alarming" postcode lottery in services, Labour has warned.
The Opposition made the comments after new figures revealed wide regional disparities in the amount of money spent on services for the mentally ill.
On average, local health authorities across England spent 10% of their annual budgets on mental health services, despite research showing that it accounted for 23% of the burden of disease, the party said.
More than 140 NHS clinical commissioning groups (CCGs) responded to Freedom of Information requests from Labour about their spending on mental health services for 2013/14.
The figures showed that places where the need was greatest were among those spending the smallest amounts, a spokesman said.
Across the country, spending ranged from 6.5% of a local health authority's budget to 18% in others, the data showed.
In Merton, south west London, it was estimated that 31% of the population had a common mental health disorder, and the local health authority covering the region spent 9.7% of its money on mental health services - just under the national average, the figures suggested.
NHS Surrey Health CCG spent 6.55% of its budget on these services despite 11.4% of people it catered for being estimated to need these services.
Meanwhile, 15.9% of patients in north west London were estimated to be affected by such problems and the local health authority invested 18% of it's budget into services for the mentally ill.
"Mental health should be treated no d ifferently to physical health, but vulnerable people face this alarming postcode lottery," Labour's shadow public health minister Luciana Berger said.
"People with mental illness shouldn't have to expect different standards of care simply because of where they live.
"Mental health services are deteriorating under this Government.
"David Cameron has broken his promise to put mental and physical health on the same footing."
Professor Sir Simon Wessely, president of the Royal College of Psychiatrists, said: " These figures reveal a mixed picture.
"Different CCGs have different levels of mental illness in their patch so we would expect some variation in spending, and it's important to acknowledge that many CCGs seem to be allocating their budgets based on need.
"What we wouldn't expect - which is extremely worrying - is that when you look at the levels of serious mental illness in each CCG compared to the levels of spending, there are serious discrepancies.
"So, two CCGs may have exactly the same level of need, but one is spending half as much as the other.
"We also have serious concerns that some of the CCGs with the highest levels of mental health need are spending significantly below the national average.
"This is having a major impact on patient care."
A spokesman for the mental health charity Rethink added: " The Government has promised to treat mental health equally to physical health in the NHS but that's nowhere near the reality on the ground.
"There is a huge gulf between the demand for services and what support is actually available to people in need.
"This means that huge numbers of people who are in crisis are waiting years for treatments such as early intervention care, which has been proven to help people get better.
"Many people are missing out altogether because the services simply aren't there.
"Others are receiving substandard care because mental health services in their area are completely overstretched.
"The Government and the NHS are responsible for ensuring that the right services are in place to meet the needs of communities, but the system is failing people with mental illness and this has to change.
"We call on the Government to act on its promise to value mental health equally to physical health, by ensuring that local spend on mental health matches local demand."
Care and support minister Norman Lamb said: "It is unacceptable to disadvantage mental health when allocating local funds.
"When the Labour government introduced maximum waiting times for treatment, mental health was not included, creating an institutional bias against mental health.
"So we've committed to introducing access and waiting time standards for mental health from next April and we're making progress towards payment systems for services that reward great results for patients."