By Emma Wilkinson
BBC News health reporter
There are around 3000 active clinical trials in the UK
Red tape is severely hampering clinical research in the UK and inadvertently "killing people", leading researchers have warned.
European legislation introduced in 2004 has led to fewer patients enrolled in clinical trials and has caused "huge delays" in research, they said.
NHS bureaucracy is a further hurdle to treatments being quickly assessed, a team of UK academics added.
Regulators agreed there were some problems with interpreting EU rules.
Despite increased funding in clinical trials in the UK, the number of trials being approved has stayed the same since 2004, when the European directive on clinical trials, designed to improve patient safety, came into force.
Additional funding is being eaten up by paperwork, monitoring, and procedures such as detailed labelling of drugs, experts said.
In 2002, 6% of trials worldwide were being done in the UK but in 2007 this was 2%.
Professor Rory Collins, co-director of the Clinical Trial Service Unit at the University of Oxford, said there was a "tick box" mentality to carrying out trials which did not take into account how risky or not the research was.
Trials of well-known and well-used treatments, such as aspirin, are being expected to jump unnecessarily through the same regulatory hoops, as new drugs.
The regulations are being over-interpreted to cover people's backs, he added.
One international trial set up to assess treatments for head injury recruited 1,200 patients from the UK in a first stage done prior to 2004 but a second stage was hampered by issues of getting consent from unconscious patients in the UK where only 100 patients were signed up as a result.
"If there's less activity, there's less evidence about how to treat patients safely, how to care for patients, how to save lives," said Professor Collins.
"The hugely increased bureaucratic burden over the last several years has made it more difficult [to do trials] and inadvertently is killing people."
Professor John Bell, president of the Academy of Medical Sciences, said clinical research was strong in the UK and was a vital part of the economy.
But agreed there were "serious obstacles" maintaining its place as a world-leader.
"The regulatory environment is much more complex and much more impeding than it was five years ago."
Professor Richard Sullivan, King's College London, said at Cancer Research UK they had calculated it would take an 85% increase in investment just to keep "business as usual".
He added that there were vast differences in how the clinical trials directive had been implemented in different countries which also made collaborating with other nations very difficult.
Professor Kent Woods, chief executive of the Medicines and Healthcare Products Regulatory Agency (MHRA), said: "I don't think the situation is quite as bad as has been painted in that the number of clinical trials is steady."
He added that there had been progress on reducing the amount of form filling in the UK but he agreed the system needed to be more flexible to take into account the risk of a particular trial.
"There is an issue about how to risk-base research regulation, and it's something we're very keen to do."
The EU clinical trials directive is due to be reviewed by the European Commission in 2010.
"Extensive work is currently being carried out not only to boost the volume of clinical trials being conducted in the UK, but also the number of patients given the opportunity to participate in this research.
"The challenge is to ensure the safety of patients and the integrity of the data as efficiently as possible."