An implant which detects cancer in the body and causes a small artificial mole to appear on the skin as an early warning sign has been developed by scientists.

The tiny patch lies under the skin and is made of a network of cells which constantly monitor calcium levels in the body.

Cancer causes calcium to rocket in the body, and when too much is detected, the implant triggers the production of melanin - the body’s tanning pigment - which causes a small dark mole to appear.

Swiss scientists from the university ETH Zurich say the device can recognise the four most common types of cancer - prostate, lung, colon and breast cancer - at a very early stage of tumour development.