For the last three years, scientists in the UK have been growing more than 150 human-animal hybrid embryos secretly in British laboratories, reports reveal.
Scientists have defended their actions, saying that the techniques can be used to develop embryonic stem cells, which can be used to treat a range of incurable illnesses.
The figure was revealed to crossbench peer Lord Alton following a Parliamentary question.
"I argued in Parliament against the creation of human- animal hybrids as a matter of principle. None of the scientists who appeared before us could give us any justification in terms of treatment," the Daily Mail quoted Alton as saying.
"Ethically it can never be justifiable - it discredits us as a country. It is dabbling in the grotesque.
"At every stage the justification from scientists has been: if only you allow us to do this, we will find cures for every illness known to mankind. This is emotional blackmail.
"Of the 80 treatments and cures which have come about from stem cells, all have come from adult stem cells - not embryonic ones," he added.
Josephine Quintavalle, of pro-life group Comment on Reproductive Ethics, said: "I am aghast that this is going on and we didn't know anything about it."
"Why have they kept this a secret? If they are proud of what they are doing, why do we need to ask Parliamentary questions for this to come to light?
"The problem with many scientists is that they want to do things because they want to experiment. That is not a good enough rationale," he stated.