Cork suffered a jobs blow yesterday when leading pharmaceutical firm GlaxoSmithKline (GSK) announced that it is to cut about 100 jobs from the workforce at its plant in Currabinny near Ringaskiddy where it employs more than 500 people.

Currabinny site director Finbar Whyte said the cuts had been forced on the company by falling sales globally for some of its products including anti-depressant Seroxat, congenital heart treatment Coreg and Parkinson's medicine Requip.

However, the single biggest factor in the move has been falls in the sales of the company's type 2 diabetes or adult-onset diabetes treatment, Avandia, which accounts for some 20 per cent of Currabinny's manufacturing output, said Mr Whyte.

Currabinny is the sole manufacturing site within GSK for the active ingredient for Avandia, rosiglitazone, and is suffering the consequence of a drop in sales of the drug after a study linked the active ingredient to an increased risk of heart attack.

A study in the New England Journal of Medicine found a 43 per cent increased risk of heart attack among those with diabetes using rosiglitazone but this was strongly disputed by GSK which said it stood over the safety of Avandia when used appropriately.

Mr Whyte said the drop in the global sales of Avandia and the other drugs had led to excess capacity at the plant. The decision to cut the Cork workforce was taken to protect the future of the plant which, he said, remained a key new product introduction site with GSK.

"This proposal is not a reflection on the performance of the site or the commitment of our employees," said Mr Whyte, adding that the company would do all it could to offer support to those likely to be affected by the redundancy programme.

The Currabinny site received a €150 million investment in 2007 and remained strategically important for the company, he said.