Britain is a "Prozac Nation" facing a crisis in mental health care, Liberal Democrat leader Nick Clegg says.
People with depression are facing long waits for treatment
He has warned the over-use of pills and poor mental health services were failing the public.
The party has obtained figures showing waits of more than two years for some counselling and psychotherapy services.
Mr Clegg said the Lib Dems would guarantee treatment within 13 weeks. The government guarantees hospital, but not community care, within 18 weeks.
In a speech to The Guardian Public Services Summit in St Albans, Hertfordshire, Mr Clegg said: "Britain has become the true Prozac Nation. I believe this trend has gone too far.
"We must cut the number of anti-depressants prescribed by doctors. Pills must not be a crutch for the wider issues in our society which cause mental health problems."
The Lib Dems questioned over 100 NHS trusts - receiving 33 replies - about the psychology, counselling, psychotherapy and eating disorders help they provide.
They asked the trusts for data on the longest waits they had for the non-emergency treatment.
Psychotherapy and counselling services had the longest waits with six trusts recording waits of more than two years. Overall, the longest wait recorded by each trust averaged out at seven months.
The findings, obtained under the Freedom of Information Act, come as hospital patients face shorter and shorter waits.
By the end of this year, trusts have to ensure all patients are seen within 18 weeks.
But this does not cover community care, such as the mental health services for people with conditions like depression.
The Lib Dems believe this should be rectified with Mr Clegg setting out a range of policies to help people needing mental health treatment.
If elected, the Lib Dems pledge treatment within 13 weeks and if that target was missed patients would have the right to private treatment.
Experts have blamed the long waits in mental health care for the soaring rates of antidepressant drug prescriptions.
More than 31m prescriptions for drugs such as Prozac were issued in England in 2006 after an almost continuous rise over the last 10 years.
Mr Clegg said he recognised there was a role for medication, but that it should not be the default option.
Paul Farmer, chief executive of Mind, said: "Three years is too long to make someone wait for help that could transform their life, possibly even save their life.
"Scrimping on basic mental health services is a false economy.
If someone can't get help when they first need it, their health will deteriorate, and they will require more intensive care later on."
Sane chief executive Marjorie Wallace said: "Only by treating mental illness as being as life-threatening as cancer or heart disease will we bring services to the front line and end the years of chronic neglect."
But a Department of Health spokesman said: "We are continuing to work towards improving access to mental health services and specifically psychological therapies, where we know capacity is particularly challenged."
She said £170m of extra funding for psychological therapies would mean an extra 900,000 will get treatment for conditions such as depression and anxiety over the next three years.
Are you affected by this story? Are you unhappy with treatment you received for mental health problems? Do you think anti-depressant drugs are prescribed too readily by doctors?
Working in mental health services I can tell you that all of our units and community teams are screaming out for staff. We can't cover our shifts properly, we don't have enough beds and shuffle patients from hospital to hospital in a permanent bed crisis. The service is not being run for the patients, nor for the staff. It's not a question of efficiency, we are on our knees through lack of resources.
Tony, North of England
I have suffered from depression most of my teenage and adult life (I am now 28) and have never once received adequate care. When it was mild depression, I was given prozac and told to exercise more, when it was severe depression I took overdose after overdose and was put on a waiting list for counselling. After waiting patiently for 2 years, I was told they'd lost my file and I had to start again from scratch. In the end I got myself in a stupid amount of debt by paying for therapy myself. I am now halfway to being "cured" but I have the added stress now of being seriously in debt!
Claire Martin, Colchester, UK
Eight years ago I developed anxiety and clinical depression and I was treated very badly by the NHS system....Drug treatment was given by my GP without any real follow up and I was not offered any form of counselling. I then used my company medical insurance and was admitted to a private clinic for treatment. The contrast in care was quite unbelievable and within a month I had made such an enormous recovery. The NHS system does not know how to treat mentally ill patients and a ten minute doctor's consultation just won't do it. People need professional help by qualified mental health experts. Depression is without doubt one of the worsed sorts of suffering that a human can endure.
Rob Parsons, Reading
Mental illness is like a mental cancer...it eats away at people and is completely misunderstood and disrespected.
Marcia Perlmutter, Woking