The world's first human head transplant has allegedly been performed on a corpse in an 18 hour operation which successfully connected the spine, nerves and blood vessels of two people.

The operation was carried out by a team led by Dr Xiaoping Ren of Harbin Medical University, China, who last year successfully grafted a head onto the body of a monkey.

Italian Professor Sergio Canavero, Director of the Turin Advanced Neuromodulation Group, who has been working with the team, said they would 'imminently' move onto a living human who was paralysed from the neck down.

He told The Telegraph that electrical stimulation of the nerves proved the operation on the corpse had been successful, and that the two people had been completely attached.

British experts accused Prof Canavero of 'egotistical pseudoscience' but the neuroscientist said details of the operation would be published in the journal Surgical Neurology International within days. He also announced plans to begin work on the first human brain transplants, which he claimed could lead to 'immortality.'

Valery Spiridonov had volunteered to become the first head transplant patient

"Everyone said it was impossible, but the surgery was successful," Prof Canavero told a press conference in Venice.

"For too long nature has dictated her rules to us. We're born, we grow, we age and we die. For millions of years humans have evolved and 100 billion humans have died. That's genocide on a mass scale.

"We have entered an age where we will take our destiny back in our hands. The first human transplant on human cadavers has been done. A full head swap between brain dead organ donors is the next stage.

"And that is the final step for the formal head transplant for a medical condition which is imminent."

The Telegraph has seen an early copy of the journal paper, which confirms that the first human head transplant has taken place on two men who donated their bodies to medical science.

Describing the surgery, Prof Canavero said the operation was split into two parts. In the first procedure, the blood supply of the donor body was attached to the brain of the recipient. Then the head was severed and the nerves and blood vessels attached to the new body using a biological glue known as PEG.

When carried out on a live person the team plans to apply electrical stimulation to encourage new nerve endings to form, before using virtual reality simulations to help the patient get used to their new body.

Prof Canavero said they would take great care to ensure the larynx nerves were not severed so that the patient would still speak with the same voice when they awoke.

"Undeniably this is huge," he said. "We are wading into unchartered territory here. It's like going to the Moon. Apollo 11 was successful, so was Apollo 12, but then look what happened with Apollo 13.

"They called me crazy, a lunatic, Frankenstein. But Frankenstein was a very ethical man by the way."

Prof Canavero shocked the world in 2015 when he said that he would be ready to transplant a human head within two years.

Although Russian computer scientist Valery Spiridonov, 33, who suffers spinal muscular atrophy, had volunteered to become the first head transplant patient, the team have since said the first trial is likely to be carried out on someone who is Chinese, because the chance of a Chinese donor body will be higher.

However Prof Canavero said his ultimate goal was to transplant a human brain, and envisaged a future where people could live forever by transplanting their brains into younger bodies, possibly cloned from themselves.

"The goal of China is to treat incurable medical conditions. My goal is life extension, because I believe ageing is a disease which must be treated.

"I call it hetero chronic parabiosis - the putting together of two people of a different age. Scientists have already shown the rejuvenating benefits of injecting people with young blood.

"If you had a young, new body, it would be able to wash the old brain with young blood, rejuvenating the brain repeatedly. You could potentially live forever."

Professor Sergio Canavero shocked the world in 2015 with his transplant plans credit: Pietro Martinello

He told reporters he would be announcing details of his plans for the first brain transplant within months.

However the scientific community reacted to the news with skepticism, claiming that a head transplant operation could only be deemed a success after a paralysed human had survived the operation and recovered.

Prof Catherina Becker, Professor of Neural Development at the University of Edinburgh, said: "While there have been very encouraging developments in the regenerative medicine field, in humans and all other mammals, spinal cord injury can currently not be repaired and after a complete transection – function below the injury never returns.

"Actual success of a head transplant must be measured by long term survival of head and body with the head controlling motor function."

Dr James Fildes, NHS Principal Research Scientist at the Transplant Centre, University Hospital of South Manchester, dismissed the announcement as 'egotistical pseudoscience.'

"Unless Canavero or Ren provide real evidence that they can perform a head, or more appropriately, a whole body transplant on a large animal that recovers sufficient function to improve quality of life, this entire project is morally wrong," he said.

"Perhaps far more worryingly, this endeavour appears to revolve around immortality, but in each case a body is needed for the transplant, and therefore a human needs to die as part of the process.

"Where does Canavero propose to get the donor body from if the goal is to tackle the laws of nature?"

Prof Stafford Lightman, Director and Professor of Medicine at the University of Bristol, added: "Even if this was practically or ethically feasible – which we just don’t know – it would be a total body transplant, not a head transplant.”