Workers at GlaxoSmithKline's Ribena factory in central England will vote on Wednesday over possible industrial action to protest at the refusal of Britain's biggest drugmaker to offer staff a pay increase.

The Unite trade union said more than 200 engineers, administrators, analysts and warehouse staff would vote on action, following unsuccessful negotiations with the company since June. The ballot will close on Jan. 14.

"It is outrageous that GSK, a world renowned, highly profitable company is offering its staff no pay increase at all in 2010. GSK can easily afford to give its staff a decent pay increase," regional union officer Christine Starling said on Tuesday.

Europe's pharmaceuticals industry is not known for industrial disputes but it has seen a spate of clashes this year as employees fight back against cost-cutting moves by companies.

Britain's second-biggest drugmaker, AstraZeneca, was hit by short-lived walkouts over pension cuts three months ago, while France's Sanofi-Aventis has been in dispute with workers over plans to axe hundreds of jobs.

Expiring patents on blockbuster drugs and growing pressure on prices are threatening future revenues across the industry, prompting a tougher attitude to labor costs by management teams.

GSK's plant in Coleford, Gloucestershire, processes billions of blackcurrants each year to make concentrate for its best-selling Ribena fruit drink, a key brand within the drugmaker's consumer healthcare division.

A company spokeswoman declined to comment.