Two thirds of doctors have said that people with depression usually cannot be offered psychotherapy within two months of them being referred because the services are simply unavailable, according to the Royal College of GPs.
Another 15% of doctors said psychotherapy is only "usually" possible within two months.
The college questioned 590 GPs in the UK under a campaign by Mind, a mental health charity, demanding better access to such therapy – the government claimed it is "working hard" with the college in relation to this.
The best form of treatment for mild or moderate depression is therapy which involves talking, according to the National Institute for Health and Clinical Excellence.
The Royal College of Psychiatrists has backed Mind's campaign, which challenges political parties to say in their election manifestos that they will offer evidence-based therapy to anyone who needs it within four weeks of them requesting it.
In 2007, the government said it had set aside £173m to increase the number of NHS cognitive behavioural therapists and has helped set up the Improving Access to Psychological Therapies programme, aiming to treat 900,000 people in England by 2010/11.
The government wants half of this number moving into a recovery period and aims to remove 25,000 of them off sick pay and benefits.