Until then, watching what you eat and exercising remains the best means of staying slim, lowering blood glucose and preventing diabetes.

Dr Iain Frame, the charity's director of research, said: "It is unlikely that any single measure used on its own will bring about improved prevention of type 2 diabetes.

The scientists said the hybrid human-bovine embryos could prove useful in pursuing treatments to prevent Parkinson's disease and Alzheimer's, as well as spinal cord injuries, diabetes and arthritis.