Scientists yesterday formally applied for permission to create embryos that are part cow and part human.
The Newcastle researchers plan to extract stem cells from the embryos that can be stud-ied for their potential to treat human diseases.
By using embryos derived from animal eggs, they hope to avoid the ethical problems of tampering with human life.
Future experiments may involve the creation of hybrid human and rabbit embryos.
The application was submitted to the Human Fertilis ation and Embryology Authority (HFEA), which regulates all embryo research, by the North-east England Stem Cell Institute (NESCI).
The Institute is jointly run by Durham and Newcastle universities. A five-strong team of scientists led by Dr Lyle Armstrong plans to carry out the work at the International Centre for Life in Newcastle. Dr Armstrong, a lecturer at Newcastle University, helped to create the world's first cloned human embryo last year.
The research involves transferring nuclei containing DNA from human cells, such as skin cells, to cows eggs.
Before this process is carried out, the cows eggs' own nuclei are removed. However, a certain amount of cow DNA remains in the mitochondria - tiny rod-like power plants that sit outside the nucleus and suppy energy.
The resulting cloned embryos are 99.9 per cent human but retain a fraction of animal genes. They are therefore classed as "chimeras" - mixtures of different species.
Dr Armstrong said: "We are very hopeful that the HFEA will grant us permission for this work, which will help us to understand more about how cells behave after the nuclear transfer process. We need this information to enable us to take this area of stem cell research to the next stage."
Stem cells are immature cells that can be programmed to form different kinds of tissue. Those extracted from embryos - embryonic stem cells - have the potential to become any part of the body, from brain to bone. In future, they could form the basis of new treatments for a host of diseases, including currently incurable conditions such as Parkinson's, Alzheimer's and diabetes.
Dr Armstrong added: "At the moment we don't know if the nuclear transfer process works well enough in humans to create useful embryonic stem cells. We need to carry out many tests to establish this and, as animal eggs are freely available, it makes sense to use these as a source of material for our laboratory work.
"Stem cell research promises huge potential medical advantages and we believe we will be working towards our ultimate goal of developing new patient therapies."
Teams at Edinburgh University and Kings College London have announced plans to seek permission from the HFEA for similar work.
A decision on the NESCI application is expected within the next few months. The scientists are ready to start work immediately if they get the green light.