GlaxoSmithKline said action taken by US authorities forcing the withdrawal of two key drugs would have an "uncertain" impact on its profits.

Glaxo, which employs more than 1,000 people in Barnard Castle, County Durham, is expected to meet US officials to resolve manufacturing issues that led regulators in the enforce the withdrawal of the drugs.

The supply disruptions led analysts to reassess their earnings forecasts and to warn that at least £140m of profits could be lost in the current financial year.

Shares have fallen more than three per cent since regulators took action against the antidepressant Paxil CR and the Avandamet diabetes treatment on Friday.

The action was taken on the grounds that the company had violated manufacturing standards at bases in Puerto Rico and in Tennessee.

Analysts at Barclays Stockbrokers said the distribution of both drugs was likely to be continued later this year, but warned that sales of Paxil CR may be damaged permanently.

They said: "The tough generic competition facing Paxil CR could dent recovery in the product's performance when it is reintroduced, but the impact on Avandamet should be relatively limited."

In a statement, Glaxo repeated the guidance it provided with its fourth-quarter results by saying it expected earnings per share growth this year to be in the low double-digits, subject to uncertainty surrounding the drugs.

Sales of Paxil CR, which is not on sale in Europe, were £396m last year and revenues from Avandamet were £222m.

Steve Plag, of broker CSFB, has cut three per cent from his earnings forecasts for this year and warned that a significant portion of the lost sales of Paxil CR would never be recovered.

A worst-case scenario would also see Glaxo fined for the violations, but Mr Plag said he saw no possibility of liability claims from customers