Health regulators have criticised drugs firm Glaxosmithkline (GSK) for withholding information over the risk of suicide relating to one of its anti-depressant drugs.
The Medicines and Healthcare Products Regulatory Agency (MHRA) said today it remained concerned that GSK failed to raise the alarm earlier over the side-effects of Seroxat.
Government prosecutors have ruled that there is no realistic prospect of getting a conviction over the issue.
But new legislation ensuring drugs companies pass on results of clinical trials promptly is to be introduced, public health minister Dawn Primarolo told Parliament.
Seroxat is the most frequently-prescribed anti-depressant in the UK, but there have been complaints that it triggers suicidal feelings in some patients.
The MHRA launched an investigation into GSK in May 2003 over allegations that it knew of the drug's dangers for several years but failed to pass the information on.
Data from an earlier clinical trial showed Seroxat was not effective in treating under 18s and had in some cases triggered a higher risk of suicidal behaviour.
Once the results were made known, the watchdog immediately warned doctors of the side effects.
Announcing the results of the subsequent investigation into GSK, professor Kent Woods, chief executive of the MHRA, said: "I remain concerned that GSK could and should have reported this information earlier than they did.
"All companies have a responsibility to patients, and should report any adverse data signals to us as soon as they discover them."
In a letter to GSK, Professor King states that a tightening up of the law will now be introduced as a result of the firm's failure to declare information promptly.
He adds: "Such a course of action should be unnecessary in an industry which relies so heavily on public trust and aspires to high ethical standards. I would have thought it self-evident that such information should be made available promptly to the regulator in order that action can be taken to protect public health.
"However, that moral responsibility now needs to be insisted upon by the unambiguous force of law."
In a written statement to parliament, Ms Primarolo announced that "immediate steps" would be taken to strengthen the law making it clear that drugs firms must disclose any information they had which could have a bearing on the protection of health.
Responding to the MHRA ruling, the minister said: "Companies that conduct clinical trials should not compromise people's health by withholding information."
Seroxat was designed to restore the taker's confidence and general happiness.
But some patients claim their lives have been blighted by addiction as a result of taking the drug, suffering serious withdrawal symptoms when trying to get off it. Others claim it has resulted in self harm or made them feel suicidal.
In a statement, Glaxosmithkline said it "notes" the conclusions of the MHRA.
Dr Alastair Benbow, medical director for GSK Europe, said: "The safe use of our medicines is paramount to everyone who works for GSK and the company is committed to ensuring that all appropriate information is made available to regulators, doctors and patients.
"We firmly believe we acted properly and responsibly in first carrying out this important clinical trials programme and then informing the regulatory agencies when we identified a potential increased risk of suicidal thinking and behaviour in patients under 18."
He added: "Whilst there are substantive and rigorous requirements in place regarding disclosure of clinical trial data, it is clear that there is a need and benefit to strengthen the confidence of decision-makers and the general public that all pharmaceutical industry clinical trial data are disclosed promptly and transparently."