A charity for men with prostate cancer says many face a "titanic" struggle to be prescribed an approved drug.
The drug blocks cell division
Taxotere can improve the quality of life of patients in the later stages of the cancer, and prolong their lives.
It was approved in June by the National Institute for Health and Clinical Excellence (NICE) for use in the NHS in England and Wales.
But each course costs about £7,000 and the Prostate Cancer Charity says some men are denied it on cost grounds.
The charity claims that some doctors have been told to ration the number of courses of taxotere that they prescribe by primary care trusts struggling with limited funds.
Taxotere was originally developed to treat breast cancer.
It has been found to extend survival time by 25% over the standard treatment for men no longer responding to hormone therapy, and cuts pain and weight loss.
More than 30,000 men are diagnosed with prostate cancer in the UK each year, and around 10,000 die from it.
Thousands of men with disease that has spread to other parts of their body are now supposed to be considered for the drug.
Call for action
John Neate, chief executive of the Prostate Cancer Charity, said "It cannot be acceptable that men and their families who are already having to deal with the tough news of a prostate cancer diagnosis, have to wrestle with NHS bureaucracy at the same time.
David Rae was diagnosed with terminal cancer two-and-a-half years ago.
He was given taxotere, in combination with another drug, on a clinical trial at Queen Elizabeth Hospital, Birmingham.
"In that six months my whole demeanour changed. My quality of life was vastly improved," he said.
I was able to get out and about, I went on holiday to Scotland, I drove down to Greece, I felt so much better.
"If you consider that I was housebound, and could not walk back in March, that was a magnificent transformation."
"Yes, there are cost implications and yes, I do understand the challenges for PCTs in balancing their books and in meeting the inexorably rising public demand for wider treatment choices.
"But we know that prostate cancer is catching up from a very low base and it deserves to be given special recognition for that in funding decisions."
Hormone therapies are typically used to treat prostate cancer, but they usually only work for up to three years.
With no further treatment, a patient might expect to live for about another year.
Another drug, mitoxantrone, can help - but has been out-performed by Taxotere in trials.
The drug, known technically as docetaxel, works by blocking the mechanism that allows cells to divide.
Taxotere can cause side effects such as flushing, skin rash, chest tightness, back pain, anaemia, nausea, sore mouth and taste change, diarrhoea, hair loss, hypersensitivity and tiredness.
Mr Neate, speaking at the National Prostate Cancer Conference in London, said patients were also being denied access to other specialist treatments, such as brachytherapy (a type of radiotherapy).
There was also a failure to provide consistent access to specialist nurses, he said.
Professor Nick James, of the University of Birmingham, said primary care trusts would not dare to treat women with breast cancer in the same way that they treated men with prostate cancer for fear of attracting negative media headlines.
"Essentially men with prostate cancer get a very raw deal. The people who make these funding decisions make them with one eye on how it is going to play in the media."
A Department of Health spokesman said: "A recent report showed an improvement in access to NICE approved drugs across the country.
"Though some trusts may be under financial pressure, and may need to make difficult decisions, this will not have an adverse effect on patient care."