By Branwen Jeffreys
Health correspondent, BBC News
NICE advises on which drugs should be bought by the NHS
Too many new cancer drugs are being turned down or restricted to small groups of NHS patients in England, the Conservatives claim.
Shadow health secretary Andrew Lansley said doctors should have a greater role in deciding which drugs to prescribe.
The party is calling for better deals with manufacturers to reduce prices.
But the government's medicines advisory body said it recommended drugs backed by clinical evidence, targeted at patients most likely to benefit.
On Saturday, Conservative leader David Cameron met with campaigners for kidney cancer drugs in his home constituency of Witney, Oxfordshire, where he outlined a plan for a cancer drugs fund.
He said since a Tory government would not go ahead with Labour's planned National Insurance increase, the £200m this would cost the NHS would instead be used to provide more people with drugs.
"We want to get drugs together more quickly," he said.
"In the UK today there are thousands of people who want a certain cancer drug, whose doctors tell them they should have one, who don't get it."
Balance of decisions
The Department of Health said in a statement that the Conservative analysis was "selective" and "misleading".
A spokesman added: "Cancer is frightening to face, tough to beat and it is important to have clear information rather than this selective way of representing data".
Not all patients with a particular condition benefit from a drug and some drugs only work really well for some patients or at a particular stage in a disease
The Tories said they were not criticising individual decisions made by the National Institute of Health and Clinical Excellence (NICE), but wanted to see a shift in the balance of decisions.
Mr Lansley said: "We've got to arrive at a point where people who have a cancer, who know there is a new cancer medicine that sometimes is clearly shown to extend life, or improve the quality of life, and their prospects, that those drugs are going to be available on the NHS."
But the chief executive of NICE, Sir Andrew Dillon, said it was wrong to recommend the use of treatments "where the additional benefit is uncertain".
"Not all patients with a particular condition benefit from a drug and some drugs only work really well for some patients or at a particular stage in a disease," he said.
Decisions on whether to recommend a drug for certain stages of a disease or for certain patients were often based on information from the European Medicines Agency, the drugs watchdog added.
The Conservatives are also calling for greater use of patient access schemes, where a drugs manufacturer typically agrees to discount the price of a new cancer treatment for certain types of patient.
How this would be achieved is unclear, as the NHS is only a small part of the global market for a new drug. At the moment NICE can only consider such schemes if they are proposed by the manufacturer.
Since November 2008, NICE has considered 14 new treatments for cancer and approved nine of them for use by NHS patients. In some cases, the drugs under consideration were to treat the same type of cancer.
A drug for advanced kidney cancer, Sutent, was recommended as the first treatment for patients in March 2009 after a vigorous campaign by doctors and patients.
But three other drugs for the same type of cancer have had their application to be used as a first line treatment turned down by NICE.