Millions of pounds of charity donations and taxpayers' money have been wasted on worthless cancer studies, the BBC has learned.
Some scientists say millions of research funds have been wasted
File On 4 has discovered thousands of studies have been invalidated.
It found some scientists have failed to carry out simple and inexpensive checks to ensure they are working with the right forms of human tumour cells.
Cancer Research UK said it used robust procedures to check the cell-lines used in research.
One of the latest examples of scientific research to be affected by this problem is a study of oesophageal cancer.
Researcher Dr Chris Tselepis worked with an international team which has found that TE7, an experimental culture of cancer cells used in labs for the past 20 years, was the wrong cancer.
"Fortunately, for us our research was based on a number of cell types, so the impact of a mistaken identity for this line has actually been fairly minimal to us," said Dr Tselepis who is studying the cancer at the Cancer Research UK laboratories in Birmingham University.
"But I'm sure there's many other laboratories UK and worldwide-based that essentially base lots of their conclusions on one cell line and in that case, this mistaken identity has a massive impact on conclusions that people draw from such studies," he added.
Few scientists publicly admit such problems but Prof Geoff Pilkington, of the University of Portsmouth, told the BBC that he had to discard research into brain tumours after it emerged his team were studying human cells contaminated by the cells of rats and mice.
"Whole programmes of research had to be redone using verified human brain tumour cells," he said.
"It's hugely expensive and it's incredibly frustrating," Prof Pilkington added.
The problem is compounded by the fact that studies based on erroneous research data will be printed in reputable scientific journals and become part of the accepted literature, thus misleading future researchers.
Earlier this year 19 eminent cancer specialists from the UK and USA wrote to the US health secretary urging tough action to end this waste of time, effort and money.
The US authorities replied that there appeared to be "abundant evidence" that many studies and publications had been compromised.
But the letter's originator, Prof Roland Nardone of the Catholic University of America, told the BBC that some scientists seemed unwilling to act.
He said the best way to get scientists to comply would be to withhold research grants and publication in scientific journals unless their research used authenticated cell-lines.
This verification can be achieved using a technique of DNA profiling which compares the cell-line with a list of known contaminants and can cost as little as £180 per sample.
But the Medical Research Council, the major source of public funds for such research in the UK which provides £70m of grants annually for cancer studies, is reluctant to enforce authentication.
Dr Rob Buckle of the MRC told the BBC: "As soon as you start talking about regulation we have to ensure that it is proportionate and does not inhibit research."
Dr Buckle said the MRC was not aware of any particular study in the UK which had been compromised by problems with cell samples.
However, one of the UK's leading cancer medicine experts has said it is time for the scientific community to put its house in order.
Cancer Research UK says it carries out stringent checks on cell-lines
"No grant or no publication," said Prof Karol Sikora, of Imperial College, London.
"If one of the leading journals, which all of us want to publish in, said: 'You have used cell-line - just give us the certificate of authenticity,' Now we can tell all that and it doesn't necessarily cost a lot of money."
Cancer Research UK, which spends £315m a year on research, would not be interviewed for the programme.
Instead it issued a statement from Dr Lilian Clark, its executive director of Science Operations & Funding, which said: "It is of paramount importance for us to ensure that all our researchers deliver world class science - they have the latest systems and robust procedures in place to guarantee this."
Dr Clark said the charity carried out stringent checks on cell-lines, including a DNA authenticating service.
To learn more about this story listen to File On 4, BBC Radio 4 Tuesday 20 November 2000 GMT, repeated Sunday 25 November 1700 GMT.