The health secretary, Patricia Hewitt, will today give a huge boost to the clinical status of nurses by promising experienced members the right to prescribe almost every medicine in the national formulary, for every type of medical condition.

In a historic move that smashes the demarcation barrier between doctors and nurses, she will outline plans for legislation to allow nurses in England to treat every aspect of a patient's illness, including diagnosis, prescription and monitoring, without supervision by a doctor.

Similar prescribing rights will also be extended to pharmacists, giving patients the opportunity to get medicines on prescription without visiting a GP.

Ms Hewitt's decision is set to cause fierce argument between the medical professions. When told of the move last night, officials at the Royal College of Nursing were jubilant. But there was outrage at the British Medical Association, which fought hard against the proposal, the most radical of five options that the government put forward for consultation in February.

Hamish Meldrum, chairman of the association's GPs' committee, said: "While we support the ability of suitably trained nurses and pharmacists to prescribe from a limited range of medicines for specific conditions, we believe only doctors have the necessary diagnostic and prescribing training that justifies access to the full range of medicines for all conditions.

"This announcement raises patient safety issues and we are extremely concerned that the training provided is not remotely equivalent to the five or six years every doctor has undertaken."

Ms Hewitt will announce her plan at the chief nursing officer's conference in London today, presenting it as an opportunity for patients to get quicker and more effective access to medicines.

Nurses and pharmacists who go through an additional training course will be able to prescribe almost any licensed medicine for any medical condition, with the exception of a few controlled drugs such as diamorphine, she will say. From spring next year, nurses will become eligible to go on the course three years after qualifying, but will require a recommendation from their employer. The extra training will last at least 38 days, a Department of Health spokeswoman said.

"The extension means specialist nurses running diabetes and coronary heart disease clinics will be able to prescribe independently for their patients. Pharmacists will be able to independently prescribe for the local community, for example, controlling high blood pressure and diabetes." This would take pressure off GPs, allowing them to focus on more complex cases and improve the availability of care.

"This means that a young person wanting to control their asthma, or a terminally ill patient being cared for at home by a healthcare team, will soon find it easier and more convenient to get the medicines they need. This is another step towards a truly patient-led NHS," she added.

Nurses were given the right to prescribe a few drugs in 2002 to help them deal with minor injuries, health promotion and palliative care. This was extended to about 240 medicines in May, but remained only a small fraction of the formulary.

Matt Griffiths, joint prescribing adviser to the RCN, said the restricted list did not include the latest medicines. "If we are given the entire formulary ... it would allow us to assess, diagnose and treat patients' conditions, putting us in charge of the complete episode," he said. "We've been asking for this for 20 years.

"This is not about being doctors. It is about being a maxi-nurse, not a mini-doctor, and providing the bast care for the patient." It was likely that tens of thousands of nurses would qualify as full prescribers in the next few years, he added.

The Royal Pharmaceutical Society said extending prescribing rights to its members would help patients get the treatment they needed during evenings and weekends when GP practices were closed.