The UK’s drugs regulatory agency said it would not prosecute GlaxoSmithKline (GSK) for allegedly withholding clinical trials data related to its antidepressant Seroxat (paroxetine), sold in the US under the brand name Paxil.

Clinical trials data have indicated that patients under 18 who took the medication had an increased risk of suicide.

The UK’s Medicines and Healthcare Products Regulatory Agency (MHPRA) said in a statement: “The legislation in force at the time was not sufficiently strong or comprehensive as to require companies to inform the regulator of safety information when the drug was being used for, or tested outside its licensed indications.”

Noting the agency’s conclusions, GSK’s medical director for Europe, Alastair Benbow said: “We firmly believe we acted properly and responsibly in first carrying out this important clinical trials program and then informing the regulatory agencies when we identified a potential increased risk of suicidal thinking and behavior in patients under 18.”

GSK gave British health officials data from clinical trials in 2003 which indicated patients under the age of 18 had a higher risk of suicidal behavior if they were treated with Seroxat compared to those receiving a placebo. The research also indicated that Seroxat was ineffective in treating depressive illness in patients under 18.

MHPRA chief executive Kent Woods said in an Assoicated Press report that he was still concerned GSK, “could and should have reported this information earlier than they did.”

“This investigation has revealed important weaknesses in the drug safety legislation in force at the time,” Woods said. “Subsequent legislation has partially addressed the problem, but we will take immediate steps to ensure the law is strengthened further, so that there can be no doubt as to companies obligations to report safety issues.”

In 2007, an Illinois judge approved a $64 million class-action deal involving Paxil.

The agreement, under which plaintiffs can get full refunds for their Paxil purchases, settles claims GlaxoSmithKline misled consumers by promoting the drug to children. Parties in the suit originally made the arrangement in November 2006, contingent on a hearing to determine whether the settlement was fair and whether plaintiff’s attorneys were entitled to the $16 million settlement fee they requested.

In 2006, the FDA issued warnings against the use of Paxil in children after studies found the drug increased suicidal tendencies while having questionable effects on depression.