NICE decides what drugs the NHS should pay for
The government is to set out plans to speed up approval of drugs used in the National Health Service in England, Wales and Northern Ireland.
The National Institute of Health and Clinical Excellence (NICE) can take up to two years to make a decision but ministers want this cut to six months.
Patients will have their legal rights to drugs recommended by NICE laid out in the planned NHS constitution.
Health trusts will no longer be able to refuse drugs on cost grounds alone.
The draft version of the constitution is expected to set out what patients and staff are entitled to from the NHS.
This includes "fundamental principles" such as universal access to healthcare, and to drugs and treatments approved by NICE.
In Scotland, the equivalent role of NICE in approving drugs is undertaken for the Scottish NHS by the Scottish Medicines Consortium (SMC).
The decision-making process is devolved from that in England, Wales and Northern Ireland and the SMC does not always make the same decisions as NICE on which drugs should be made available.
The approval process in Scotland has proved to be quicker owing to the imposition of three-month targets for initial decisions by the SMC.
A Department of Health spokesperson said there was a "perception" that some treatments approved by NICE were not universally available and the constitution would make the legal rights of patients clear.
Health Secretary Alan Johnson said: "What we have heard from patients is that one of their major concerns is the perceived 'postcode lottery' in access to drugs - that there are too many variations around who gets access to prescribed drugs and that these variations are a lottery depending on where you live.
"The draft constitution will address this by making it explicit that patients have the right to NICE-approved drugs if clinically appropriate."
Speaking on The Politics Show on BBC One, he said primary care trusts would no longer be able to refuse drugs or treatment which have been approved by NICE - with £100 million being provided from central funding for drugs and treatments.
Trusts will be required to look at the evidence on efficacy and cost effectiveness and give detailed explanation to patients refused treatment recommended by their doctors.
Conservative health spokesman Andrew Lansley said the change would not be significant, although he hoped patients would get faster access to drugs.
"When you look at comparisons with this country and other countries it is frankly scandalous. We have some of the best cancer research in the world in this country but we have amongst the slowest uptake of new cancer drugs, and we have one of the poorest five-year survival rates for cancer."
Patients Association vice-chairman Michael Summers told BBC News the new rules needed to be made crystal clear so that there was no room for varying interpretation.
"I just hope that the constitution will spell out sufficiently clearly for primary care trusts what they can get away with and what they can't," he said.
"One of the problems related to the provision of drugs is the delays. NICE were doing their best but in some cases new drugs would take three years to come on to the market."
The issue of access to new, often expensive drugs, on the NHS has been a contentious one.
Roy Lilley, a former director of an NHS trust and independent health policy analyst, told the BBC you cannot take the cost of drugs out of the equation.
He said: "We have to ask ourselves the question: will drugs get more complex? Yes. Will they get more expensive? Yes.
"To say that we will buy them whatever, however much they cost, you might as well give the pharmaceutical industry a blank cheque. It's a huge worry.
"There are some fantastic drugs. I'm not saying we shouldn't have them. But there has to be a rationale behind the use of resources.
"You can't say because it's here we're going to buy it, that's crazy."
Much of the delay in assessing a new drug has been pinned on the failure of government to refer them to NICE quickly enough.
The most controversial drug to go through the process has been the breast cancer therapy Herceptin.
It was finally approved by NICE in 2006 after a number of patients had taken their primary care trust to court over their refusal to fund treatment.
Some have also argued that patients should be allowed to pay for treatment not approved for use on the NHS without losing their right to NHS services.
Ministers in Wales, Scotland and now England have begun reviews into whether these "co-payments" should be allowed alongside NHS treatment - however, the subject will not be addressed by the new constitution.
Lord Darzi, a practising surgeon as well as health minister, is due to publish his review of the NHS on Monday.