Propranolol, a drug commonly prescribed for high blood pressure can erase bad memories, new research has shown.

The discovery could lead to new ways of treating the emotional after-effects of traumatic experiences such as terrorist attacks or natural disasters, researchers say.

In a study published in the journal Nature Neuroscience, a team of Dutch researchers created a fearful memory in 60 participants by associating pictures of spiders with a mild electric shock.

When the beta-blocker drug propranolol was provided before again showing the photos of spiders, there was a marked reduction in how startled the individuals were.

The effect appeared to be permanent, the researcher said.

Amsterdam University professor Merel Kindt, who led the study, wrote: 'Millions of people suffer from emotional disorders and the relapse of fear, even after successful treatment.

'Our findings may have important implications for the understanding and treatment of persistent and self-perpetuating memories in individuals suffering from emotional disorders.'

However, Dr Daniel Sokol, a lecturer in medical ethics at St George's, University of London, said: 'Removing bad memories is not like removing a wart. It will change our personal identity since who we are is linked to our memories. We must reflect on the knock-on effects that this will have on individuals, society and our sense of humanity.'

John Harris, Professor of Bioethics at the University of Manchester, said: 'An interesting complexity is the possibility that victims, say of violence, might wish to erase the painful memory and with it their ability to give evidence against assailants.'