The behaviour of Boots and Mothercare contrasts with that of manufacturers, who have quietly stopped putting bisphenol A, or BPA, into baby bottles "to allay parents' fears", amid peer-reviewed studies in medical journals associating it with serious health problems in laboratory animals.
Canada and three US states, Connecticut, Minnesota and Wisconsin, have banned BPA in baby bottles and the US Food and Drug Administration ( FDA) says it is concerned about its impact on babies and young children, and supports its removal from infant-feeding products.
However BPA, a synthetically-produced hormonal substance which is added to plastics to make them tougher, is legal in the UK and most of the rest of the world, and Boots and Mothercare have continued to sell off old stock containing the controversial chemical without labelling it on packaging.
Boots also sells BPA bottles branded with Disney characters made by another firm, Tommee Tippee, which has removed BPA from its own bottles.
In the US, the six biggest baby bottle firms including Disney stopped making BPA products last year following scientific outrage at the then failure of the FDA to tackle its potential impact. Other infant-feeding brands such as NUK have already removed BPA from bottles.
Boots, Mothercare and Disney insisted BPA bottles were safe, even though they have ordered its removal from current production. Mothercare said: "Mothercare takes the issue of product quality and safety extremely seriously and all our bottles and feeding equipment comply with strict European standards."
It added that it offered "reassurance and advice" to customers through its website and leaflets, which advise users to ensure polycarbonate bottles were "free from scratches or signs of wear, to replace them after six months' usage and not to use boiling water".
But Mothercare admitted that it was only continuing to sell BPA bottles because its timetable for removal had slipped. The retailer had planned to stop selling BPA bottles by January 2010; now the target was "the end of the autumn".
Mothercare said: "We anticipated that there would be a phasing-in period, during which time the new BPA-free stock would replace the previous ranges. However, the timescale of that phasing-out period has taken longer than we originally expected and we now anticipate that all our stock in stores will be BPA-free by the autumn."
Boots, owned by the private equity company KKR, said: "With the exception of Canada, polycarbonate, which is made from bisphenol A, is approved as a food-contact material worldwide. The vast amount of scientific evidence still supports its continued safe use."
Disney acknowledged that parents here were being offered different products to their counterparts in the US, where its BPA bottles are no longer on the shelves. By contrast, colourful Winnie-the-Pooh-branded bottles made last year are still on sale in the UK, three months after their last production date.
A Disney spokeswoman, Sandra van Vreedendaal, said: "As far as Europe is concerned they have said that amount of BPA does not pose a threat to human health. They consider the use of BPA to be safe. However we have decided to move to totally BPA-free with a final target of 2010. A number of our products in Europe are already BPA-free."
She added: "No Disney-branded Tommee Tippee products have been manufactured since 1 January, so any products in the market are old stock and will be phased out in time."
Breast Cancer UK has launched a campaign calling for the removal of BPA from baby products. Clare Dimmer, chair of trustees at the charity, said: "It's amazingly cynical that, despite the serious health concerns surrounding infant BPA exposure, retailers and manufacturers still find it perfectly acceptable to continue to sell BPA stock here despite similar products already being withdrawn from sale in the US and Canada.
"I think parents will be irate about these double standards and disappointed that retailers are not taking on board the full advice from scientists."
According to independent scientists, BPA may be an underlying cause of a collection of illnesses rapidly rising in the West, including obesity, heart disease, diabetes, fertility problems and birth defects. Concern is greatest about its transmission from pregnant mothers to babies in the womb, and on young children.
One of a class of chemicals known as endocrine disruptors, BPA interferes with the release of the female hormone oestrogen, and its impact is greatest on disorders associated with metabolism, fertility and neural development.
BPA is widely available in tins of food and canned drinks, where it is used to toughen the internal lining of tins. It is also used in a wide array of plastic products such as mobile phones, computers and medical equipment.
Hundreds of studies have been conducted on BPA, most of which have found harm to laboratory rodents and primates, and studies looking at the effects of BPA in humans have also found links to ill-health.
However, several studies funded by the chemical's manufacturer and involving large numbers of laboratory rodents have given BPA a clean bill of health. Regulators such as the Food Standards Agency have relied on this small number of industry-based studies in reaching their assessments that BPA is safe.
However, in January, the US FDA reversed its long-held position that BPA was harmless and announced it favoured its withdrawal from baby bottles – and would support the canning industry's search for alternatives.
Scientists have claimed that the American chemical industry has been overly powerful in its influence on the FDA, sparking a backlash from independent scientists prior to its U-turn. In December, seven experts from five British universities including London, Ulster and Stirling wrote to the Health Secretary Andy Burnham calling for a review of BPA.
A spokeswoman for Born Free, one of many BPA-free brands, said: "We believe that BPA has been one of the most studied chemicals for decades for a reason. Recent scientific research suggests that small amounts of BPA may leach into foods or beverages stored in polycarbonate containers, especially when the contents are acidic, high in fat, or heated.
"Research also suggests that BPA may act as an endocrine disruptor, a substance which mimics natural human hormones, and that babies and growing children are particularly at risk from exposure because they are still undergoing many hormone-mediated developmental processes.
"We believe that the use of BPA in baby-feeding products should be banned in its entirety. It is for this reason that our entire product portfolio has always been and always will be free from harmful chemicals such as BPA."
Breast Cancer UK's Ms Dimmer added: "Several hundred independent scientific studies have been published in peer-reviewed academic journals over the last decade that have established the low-dose effects of BPA.
"These studies include research conducted on cell cultures as well as mammalian animals and have identified potential increased risks in a whole host of chronic health conditions, including breast and prostate cancer, liver disease, diabetes, obesity, and even a potential impact on brain function. Scientists have also identified that young children and infants have the highest levels of exposure to BPA as they are less able to clear this chemical from their bodies."
She added: "This is especially troubling as infants and young children are in a rapid state of growth and development, and are potentially more susceptible to risks of exposure to BPA."
Professor Vyvyan Howard, professor of bioimaging at Ulster University, said regulators should adopt the precautionary avoidance of bisphenol A. "With our own children, who were breast-fed, we obtained glass feeding bottles for water and fruit juice," he said. "I consider that the weight of evidence is such that routine use of polycarbonate products should be avoided during pregnancy and for young infants."
A spokesman for Cancer Research UK said the evidence on BPA was insufficient to alarm parents. "No direct link between bisphenol A and breast cancer risk has been shown in humans," he said. "Some results from animal studies or work on cells in the laboratory point to the need for more research in this area.
"We acknowledge that there are some concerns about bisphenol A and its effects on other areas of human health. But it would be wrong to worry women unnecessarily about their risk of breast cancer based on what we know."