A leading British geneticist has admitted to being "really scared" by the prospect of rogue IVF clinics adopting powerful new gene-editing techniques to alter the DNA of babies.
Professor Robin Lovell-Badge fears that in places where regulation is weak, parents with enough money will soon be able to pay for inherited diseases to be edited out of their offspring.
This is just the sort of scenario critics claim would be the start of a slippery slope towards designer babies customised to be more physically attractive or intelligent.
The professor works at the Francis Crick Institute in London where a colleague has been granted permission to use gene editing to study early human development in the womb and the causes of miscarriage.
The technique, known as CRISPR/Cas9, allows scientists to "cut and paste" DNA so that highly precise changes can be made in the genetic code.
Questioned at the annual meeting of the American Association for the Advancement of Science (AAAS) in Washington DC, Prof Lovell-Badge said: "I'm very, very concerned about this. This whole notion of rogue clinics is something that has occupied fertility science for many years where these clinics have cropped up in many different countries, including the US, which are offering treatments with no real basis in science and may be dangerous in some cases.
"You can quite easily imagine that if you were to apply these gene-editing techniques then the places it would happen would have to be associated with IVF clinics. In the UK we are lucky to have good regulation but in many countries there is no regulation, or minimal regulation.
"You can quite easily imagine a combination of egos of the person running the thing and someone who wants to have treatment and has enough cash saying, 'I'll give you 50,000 dollars or whatever' - and that scares me, it really scares me. It's bad for the field."
Prof Lovell-Badge took part in an international summit on gene-editing held in the US capital in December. The participants, who included leading scientists, ethicists and policy makers, concluded that carefully regulated gene-editing for research was justified.
His concerns were echoed by fertility pioneer Lord Winston, Professor of Science and Society at Imperial College, London, who went further, arguing that the use of gene-editing by IVF clinics was not likely to be confined to countries with poor regulation.
Lord Winston said: "Whatever is said, regulation cannot prevent this from happening either in the UK eventually or much more likely elsewhere. Robin has a rather touching faith in the ability of bodies like the HFEA (Human Fertilisation and Embryology Authority) but I am not so convinced.
"With the power of the market and the open information published in journals, I am sure that humans will want to try to 'enhance' their children and will be prepared to pay large sums to do so."
Bio-ethicist Dr Sarah Chan, from the University of Edinburgh, argued that infants with medical genetic enhancements should not be regarded as "designer babies".
She did not think that genuine designer babies, altered to improve intelligence or physical characteristics, were inevitable.
"From a UK context we ought to feel confident that if and when we get to the point that the technology is sufficiently advanced, we will approach it appropriately," said Dr Chan.
"I would venture to say that for a lot of people it may not be a scary prospect, because the first context in which we're likely to see this would be in the clinic for reproduction would be ... to cure or to attempt to alleviate serious disease."
Canadian professor and philosopher Francoise Baylis, from Dalhousie Medical School, who also attended the gene-editing summit and spoke at the AAAS meeting, did not agree.
She said: "It's a very real worry that many of the activities in the area of human reproduction have moved forward without proper clinical trials which has meant that we don't actually have data that is robust in the clinical context.
"Any one country can start to look like a rogue-technology place.
"It's not likely to be a top-down initiative, it's likely to be a bottom-up initiative, which is different to the types of concern we've heard before about eugenics."
She added: "We allow parents to enhance their children already through all kinds of social interventions, such as access to higher education, so there is already a belief or orientation that that is a proper goal or objective for a parent which is to give their children as many opportunities as possible ..
"Are people going to start focussing on something like stature? We have good data to show that if you are a taller male you will do better than a shorter male. We know that to be true ... we might say let's just fix it, let's make people taller."