The Department of Health is to announce new curbs on use of the antidepressant drug Seroxat, in response to claims that it has pushed some people to suicide and caused withdrawal problems in others.

At a press conference to be chaired today by Professor Alastair Breckenridge, head of the Committee on Safety of Medicines, the department will issue "new prescribing advice" for doctors and patients on the drug.

The move comes after reports that GlaxoSmithKline, the makers of what is Britain's most widely prescribed antidepressant, withheld nine studies showing that it could provoke suicidal tendencies and other symptoms in people under 18 years of age.

The Medicines and Healthcare Products Regulatory Agency (MHRA) is understood to have asked GlaxoSmithKline to contact GPs to warn them of the danger to young people. Although the drug is not licensed for use by those under 18, doctors have discretion to prescribe it on a "named patient" basis to individuals for whom they deem it appropriate.

Seroxat is one of the biggest-selling drugs in the world and was prescribed to 400,000 people in Britain last year. It is one of the class of antidepressants known as selective serotonin re-uptake inhibitors (SSRIs), of which the best-known example is Prozac, though this is less popular than Seroxat.

Seroxat and the other SSRIs were marketed because they were believed to be safer and cause fewer side-effects than older antidepressants. But persistent reports of adverse reactions involving Seroxat culminated in the MHRA setting up an independent expert panel to review its safety.

The move came after a BBC Panorama programme last autumn about problems with the drug provoked 67,000 phone calls and 1,400 e-mails, the largest response in the programme's history.

However, in a move that embarrassed the medicines regulator, the panel appointed last December was disbanded in March after several members were revealed to have links to the drugs industry. A new panel was appointed last month and today's announcement has come surprisingly soon. A Department of Health spokeswoman said it was in response to "early findings".

Reports yesterday said that the discovery of the nine studies withheld by GlaxoSmithKline had led the MHRA to order clinical auditors into the company to demand access to all its files on Seroxat. The Department of Health denied that this was imminent but did not rule it out. "We cannot say what may happen in the future," the spokeswoman said.

The reports quoted a source at the MHRA saying that the decision to send in auditors to the company was "very, very unusual" and that, normally, the agency and the companies had a good relationship.

The expert panel set up by the MHRA is investigating claims that in a small number of cases Seroxat and similar SSRI drugs may have caused people who were not previously suicidal to kill themselves. It is also investigating claims that a larger number of people have had difficulty coming off the drug and have experienced withdrawal symptoms.

The disclosure comes as the company is reeling from adverse publicity over the proposed £22m severance deal for its chief executive, Jean-Pierre Garnier. It has also been embarrassed over the battle with aid agencies and developing nations over the cost of drugs for HIV and other diseases.