A drugs manufacturer has been criticised, but not prosecuted, over claims that it withheld information about the increased risk of suicide for children taking Seroxat, the bestselling antidepressant drug.

Ministers have promised to tighten laws that require pharmaceutical companies to disclose data from clinical trials after a report suggested that GlaxoSmithKline (GSK) knew about safety risks but failed to report them to the medicines safety watchdog for five years.

GSK should have been much quicker to raise the alarm on the risk of suicidal behaviour associated with the drug in under18s, the Medicines and Healthcare products Regulatory Agency (MHRA) has found.

But after a four-year investigation involving a million pages of evidence, the agency has said that it would take no legal action against the company because it has no realistic prospect of securing a conviction.

GSK submitted data from clinical trials to the MHRA in May 2003 showing that patients under 18 had a six or sevenfold increased risk of suicidal behaviour if they were treated with Seroxat than if they received a placebo. Data also showed that the drug was not effective for treating depression in children and adolescents. Leaked documents suggested that GSK had known about these results as early as 1998.

Seroxat is the most frequently prescribed antidepressant in Britain and among the selective serotonin reuptake inhibitors (SSRI) group of drugs that account for 16 million prescriptions a year. It was subsequently banned for use in under18s.

GSK rejected claims that it had improperly withheld trial information about the drug.

Kent Woods, chief executive of the MHRA, said yesterday that the agency was disappointed that the company had not given it the information earlier, adding that drug companies had an “ethical responsibility” to do so.

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