A shortage of donor bodies is putting medical teaching at risk, the Royal College of Surgeons has warned.
Surgical students need to practice on cadavers
About 1,000 bodies are needed every year to teach anatomy to medical students, it is estimated.
But the college predicted a 30% national shortfall in the number of bodies needed by medics in the current academic year.
London is faring the worst, with a 40% shortfall expected among the capital's five medical schools and the college.
Last year the Chief Medical Officer wrote to doctors asking them to encourage patients to leave their bodies to medical research.
By law, medical schools may only accept bodies from individuals who have made a specific request for their bodies to be bequeathed for medical study.
And the Human Tissue Act now requires a witness be present.
The college said that while many people carry donor consent cards, they may not be aware of - or are reluctant to undertake - the necessary procedures for donating their bodies to medical schools.
It added that the problem may get worse in the future as many of the bodies which are donated are unsuitable, because of the effect of hospital infections such as MRSA and increased levels of surgical intervention as people live longer.
Undergraduates already receive much less teaching in anatomy than they used to, and several medical schools have abandoned dissection-based teaching altogether.
Other schools rely on giving students demonstrations using pre-dissected specimens rather than allowing them to perform their own dissections.
Dick Rainsbury, the RCS director of education, said: "The college currently receives about 60 cadavers a year.
"They are hugely important to us in the teaching of anatomy."
He added that trainees who had only watched operations rather than personal experience may not have the same degree of competence or confidence.
"Visual demonstration is not enough. If the UK is to produce high-quality surgeons, the teaching of anatomy has to be of the highest standard."
Pat Honeysett, who lives in South London, has made the necessary arrangements for her body to be donated to medical training after her mother did the same, and would urge others to follow her example.
"Once you die the body is of no use and the medical profession need to be able to practice in readiness for when they are faced with the real thing."
Emily Rigby, chair of the British Medical Association students committee, said medical students were worried about the drop in donor bodies.
"Students very much value the use of cadavers.
"It will have an impact on their understanding of anatomy and we hope to encourage the number of people donating bodies."