A £500m medical research laboratory in the heart of London could carry out work on the world's most deadly diseases, Guardian Education has learned. Backed by the prime minister, the lab, to be built yards from the St Pancras Eurostar terminal and the British Library, will replace the National Institute of Medical Research (NIMR) in Mill Hill, which includes one of the UK's 10 category 4 labs. These have the highest security level and work on highly contagious and incurable diseases such as Ebola and Lassa fever. The government also has around 350 category 3 labs where work on Sars and HIV takes place.

The potential threat of terrorism - as well as the ongoing investigation into the biosafety breaches at the Pirbright laboratory in Surrey, which caused last year's outbreak of foot and mouth disease - mean a decision to build a category 4 lab in the King's Cross area by 2013 could cause a political storm as London gears up to host the Olympics.

While most experts agree that security and safety at high-risk labs in the UK is very good, there is debate about whether they should be sited in major conurbations. Siting a secure lab in a remote field makes any outbreak easier to contain, but could limit its usefulness to scientists and hospitals.

Tough standards

Most labs are subject to at least yearly safety inspections by their regulatory body and must meet tough security standards set out in the Anti-Terrorism Crime and Security Act 2001. "People don't need to be alarmed; these labs can be run safely," says Professor George Griffin, chairman of the Health and Safety Executive's (HSE) advisory committee on dangerous pathogens.

Griffin, who is leading a study for the Health Protection Agency to chart the UK's category 4 labs, said putting a high-security lab in any conurbation should be avoided, but added: "It should be viewed in the context of a risk assessment. There may be compelling reasons for locating a laboratory at a particular site; for example, a hospital may need facilities for diagnosing haemorrhagic fever.

"Any category 4 laboratory, wherever it is located, would undergo a very rigorous multi-factorial risk assessment. It would ask what is the science being done, are there any risks to people and the environment, and what is the availability of expertise? The risk assessment would be done before making decisions." The four partner organisations in the project - the Medical Research Council, the Wellcome Trust, Cancer Research UK and University College London - are considering their options. "Detailed decisions on what the centre will contain, including whether or not to include a category 4 lab, have not been finalised. This is the work of the project's science planning committee, made up of eminent scientists and experts in their fields, led by the Nobel Laureate Sir Paul Nurse," a spokesperson says.

The partners have shortlisted architects and, after a choice has been made, they will apply to Camden council for planning permission. This week the partners are holding a series of open meetings for local residents. They will be hoping to avoid the sort of row that has broken out in the US city of Boston over the 2005 decision to build a high-security university lab.

The King's Cross project will focus attention on the safety record of category 4 labs sanctioned to work on human pathogens by the HSE, such as the military Defence Science and Technology Laboratory at Porton Down and the National Institute for Biological Standards and Control in Potters Bar, Hertfordshire, as well as labs licensed by the Department for Environment, Food and Rural Affairs (Defra) to handle animal pathogens, such as the H5N1 avian flu virus. These include the Institute of Animal Research at Pirbright, the Veterinary Laboratories Agency in Surrey, and the NIMR at Mill Hill.

The last time a breach involving a human pathogen occurred on the scale of the animal disease breach at Pirbright was in the 1970s, when two laboratory workers died after becoming infected with smallpox at the London School of Hygiene and Tropical Medicine. But a Guardian analysis of the HSE's enforcement history has found over 70 dangerous incidents in labs and breaches of health and safety regulations aimed at controlling dangerous pathogens over the past 10 years, including the potential exposure of lab workers and others to a deadly form of pneumonia, and poor safety measures in work being carried out on a category 4 pathogen.

Over the past 10 years, the HSE has brought five separate prosecutions for severe failings in safety measures at universities, research institutes and labs attached to hospitals. Imperial College London was prosecuted twice in 1998 and fined a total of £45,000. In one case, Imperial failed to seal a laboratory to allow it to be disinfected safely, and in the other incident Imperial failed to implement appropriate containment measures for work on a genetically modified virus. Since then, it has been issued with an improvement notice in 2003 for faulty disposal of genetically modified micro-organisms.

The University of Edinburgh was prosecuted for failing to undertake risk assessments and establish a genetic modification safety committee, and fined £3,500. The University of Birmingham was prosecuted for failing to ensure its air filtration and ventilation systems were up to scratch, and fined £10,000.

The HSE has also instigated three crown censures in the past 10 years, which allow it to act against government establishments that are immune from prosecution under health and safety law, such as Porton Down and the Central Science Laboratory in York. In the past five years, the HSE has issued at least 17 improvement notices and six prohibition notices for laboratory breaches of regulations governing the control of substances hazardous to health, genetically modified micro-organisms and health and safety. In addition, 42 investigations into reports of injuries, diseases and dangerous occurrences in labs have taken place since 2004. Many of these are minor accidents, such as spilling bottles containing the bacterium that causes tuberculosis in cattle. Others cases are more serious. At one unidentified institution, researchers were potentially exposed to avian flu in two separate incidents in 2006 due to needle stick injuries.

Accidents do happen

"Accidents happen. It doesn't matter if you are driving a car or working in a lab, one day something will happen," says Dr Ellen Nisbet, a malaria researcher at Cambridge University. "We are extremely well trained in what to do. If we were not you would probably see a lot more accidents.

"But if an accident does happen, it could be catastrophic. You just have to make sure it does not happen or locate the lab in an area where it is not so catastrophic if it does happen."

Professor Steve Smith, principal of Imperial College's medical faculty, says there is a general recognition that the UK needs more category 4 labs. "The question is, do you put them in the middle of nowhere or where the researchers are? If the labs are in an isolated field site, you lose proximity to the researchers and this gives a narrow view. But it is a very difficult question: how secure is secure?"

Professor Alan Malcolm, chief executive of the Institute of Biology, says if the proper safeguards are in place, locating a category 4 laboratory in central London ought to be as safe as anywhere.

"The issue is: are we certain the various safeguards and criteria are being monitored correctly? That was the issue at Pirbright. They knew the risks, but it was not being monitored properly or enforced. Responsibility is now being transferred from Defra to the HSE, which is an improvement," he says.

But a project like the King's Cross lab is inevitably political. Malcolm adds: "I find it difficult to believe that the government, if faced with being asked if it is prepared to have a category 4 lab at King's Cross, would let it go ahead. I can't see any minister standing up and putting their hand on heart and saying that, especially after Pirbright."