The whole slant of what they are saying is wrong

Dr Victoria Wilson, Cancer Research Campaign

It also claimed there may never be a "magic cure" for many forms of cancer, and said efforts should instead be concentrated on prevention.

Chemotherapy involves treating cancer cells with drugs designed to kill them.

In its response to the ASA, the CPRT claimed pathologists made mistakes and that many cancer patients with long survival rates possibly never had cancer.

Views 'unchanged'

In its judgement, the ASA said the CPRT "did not substantiate that chemotherapy was ineffective".

The ASA said there should have been independent scientific evidence to substantiate such a claim, but welcomed the trust's assurance it would not be repeated.

But the trust, founded in 1973 to provide information about cancer prevention, said it would not change its views.

Founder Victor Fallas said: "Studies have been made comparing cancer patients who have been treated by surgery with patients who were left untreated; survival was the same whether the patients were treated or not.

"No such studies have been carried out with chemotherapy and marginal studies which have been carried out comparing different cytoxic [cancer killing] agents have only shown a life extension of three to four months."

Mr Fallas told BBC News Online: "These views are perhaps revolutionary, but it will open up discussion."

'Inaccurate and depressing'

But Dr Victoria Wilson, Cancer Research Campaign (CRC) science information officer, said the trust's views were "completely misleading, negative and not at all helpful to anyone".

She added: "It is inaccurate and depressing to say chemotherapy cannot help when people fighting the disease need to remain positive.

"The whole slant of what they are saying is wrong.

"If someone was just about to start chemotherapy, or their loved one was, it would be an extremely upsetting thing to read."

She said chemotherapy was able to improve the quality and prolong the life of cancer patients.

She added the group was right to suggest there were many causes of cancer, some of which were understood, such as smoking and lung cancer.

But she said it was unlikely all its causes would be understood and that cancer would be completely preventable.