Dr Michael Macnamee, director of operations at Bourn Hall in Cambridge, where Louise Brown, the first test-tube baby, was conceived, said such entreaties "exploited the devastating emotions which surround infertility".
The Kentucky-based website, "Conceiving Concepts", tells prospective parents that embryo adoption is a "lower cost" option than in vitro fertilisation treatment and "comes with little or no paper- or legal work".
British couples wishing to follow the advice would probably need to travel to the United States to obtain a "cheap" embryo, as it is unlawful to import embryos into Britain.
Embryo adoption is the term used when a couple who are both infertile receive a spare frozen embryo created by another couple during their own in vitro fertilisation. The biological parents have to give their permission for their embryo to be used in this way.
Julie Watson, a fertility consultant who runs Conceiving Concepts, does not organise embryo adoption herself but gives couples information on where to go for treatment. "The cost can range from $500-$1,500 [pounds 300-pounds 900] per cycle," she said. "It usually has a 10 -15 per cent success rate. I'm not involved in doing embryo adoption myself. I am just giving information about what embryo adoption is and how to go about getting it."
In Britain, embryo adoption is tightly regulated. Various centres such as Bourn Hall, the Midlands Fertility Services and the Centre for Assisted Reproduction at Park Hospital, Nottingham, carry out the procedure.
Dr Macnamee said Bourn Hall's success rate was the world's best but treatment cost pounds 1,600 per cycle at his clinic and he could only think that such low prices meant clinics were offering to sell embryos rather than including the price of treatment. "It is not possible to treat someone for $500 ... It is a scandalous trade in gametes," he said.
A spokesman for the Human Fertilisation and Embryology Authority said that, at present, embryo adoption was not widespread. However, the authority could not prevent people going abroad for treatment.