Stem cells in umbilical cord blood have been used to treat blood disease
A clampdown on unproven and potentially unsafe stem cell research is being called for by an expert group.
Bionet, a group of expert Chinese and European doctors, lawyers and bioethicists, says countries throughout the world must develop more effective regulation for this emerging science.
They say desperate patients are being subjected to a huge amount of hype when they travel abroad for treatments.
The only way to counter that is through proper clinical trials, they say.
Professor Nicholas Rose, from the London School of Economics, who led the group, said Bionet's team had talked to physicians in China and Europe because China had now overtaken India as the place where pharmaceutical companies were carrying out most of their trials.
They had provided a wealth of anecdotal evidence about their concerns that stem cell research was being moved too rapidly into clinical practice without proper study.
He said: "The key is informed consent. Doctors should be able to tell the patient about the short-term and long-term prognosis and the things we don't know about the risks."
Bionet is recommending that the safety and efficiency of stem cell treatments is investigated through state-of-the-art clinical trials before they are offered to patients.
It also says doctors should be honest about the conditions under which germ cells, embryos or embryonic tissue has been collected.
It also recommends that they should only be imported and used for research if they were collected under conditions which are either similar or equivalent to those in the receiving country.
Brian MacNeill who went to China twice for stem cell treatments
Nobody should be coerced by unfavourable circumstances or by being dependent on someone to donate cells or tissue for research, banking or treatment purposes, Bionet says.
And there should be quality standards for stem cells used in clinical practice.
These should include the bacterial and viral contamination applied during the production of the stem cells.
China introduced new regulations in May calling for clinical trials before stem cell treatments were offered to patients.
Professor Qui Renzong, vice-president of the ethics committee at the Chinese Ministry of Health, said: "In China there are about 150 institutions now providing stem cell therapy for diabetes through to spinal injuries."
Foreign patients were paying an average of $25,000 (£15,434) he said but since the regulations were only recently introduced there was no way of knowing how many foreigners had made trips to China for treatments.
One patient who did go to China is 39-year-old Brian MacNeill, from Argyll, on the west coast of Scotland.
He sufferers from hereditary ataxia, a muscle-wasting neurodegenerative disease.
Mr MacNeill said: "All I can say about the treatment I had with stem cells in China was that I felt a great benefit after the first lot of four injections, with lots of therapy as well, and good benefit from my second visit about one year later.
"The second visit was needed as I felt some of my symptoms come back after 10 months and now the second visit has lasted around 14 months.
"I now am feeling symptoms come back but cannot afford to go for more stem cells. If I could I would.
"It's better to feel good now when you have an illness than be somebody very unhappy and ill anyway without even trying."
A Department of Health spokesperson said: "Any new therapy or treatment requires carefully controlled and evaluated clinical research before it can be considered safe and effective.
"In the UK, there is strict regulation to ensure that vulnerable patients are not exploited or put at risk.
"When stem cell 'treatments' are based overseas, regulatory oversight and jurisdiction is particularly problematic.
"We take this very seriously and strongly encourage anyone considering participating in overseas stem cell 'research trials' or buying internet treatments to talk to their doctor and follow health guidelines."