People with mental health problems are having to wait a "scandalously long" time for treatment and too many are only offered antidepressant medication, the Liberal Democrats have said.
Lib Dem leader Nick Clegg attacked the government's record of "shameful neglect" on mental health services.
The party found some patients have to wait up to three years for treatment, with doctors resorting to prescribing record numbers of antidepressants.
In a speech to the Guardian Public Services Summit this morning, Mr Clegg said: "Medical professionals want to prescribe effective, long-term solutions, but in the absence of those solutions it is no wonder record levels of drugs are being prescribed.
"Britain has become the true Prozac nation. We must cut the number of anti-depressants prescribed by doctors.
"Medication does have a role to play in tackling mental health problems, but they should not be the default option because of a lack of access to psychological therapies."
Based on a survey of Mental Health Trusts in England, the Lib Dems concluded there were wide variations in waiting times, driven by region and type of treatment.
In one area people had to wait for more than three years for psychotherapy.
To amend this, Mr Clegg is calling for a maximum waiting time of 13 weeks between referral and first appointment for treatment.
At present the most vulnerable patients are being forced to wait "scandalously long" for treatment when the evidence suggests early intervention is vital, he said.
Mr Clegg continued: "I am calling for nothing less than a revolution in how we treat mental illness.
"Within four years I want our health service to guarantee that no one will wait longer than 13 weeks for their first treatment. The NHS must deliver that service, or the patient will be entitled to go private."
Mr Clegg also joined mental health campaigners in condemning the continued practice of mixed sex wards.