A pharmaceutical firm is refusing to tighten security at its North-East plant, despite a break-in by animal rights activists at the weekend.

Bosses at GlaxoSmithKline, in Barnard Castle, County Durham, said yesterday that security at the site would remain as it is.

Four members of the campaign group Stop Huntingdon Animal Cruelty (Shac) spent about 20 minutes at the site, shouting at employees and handing out leaflets, after getting through security gates on Saturday evening.

They were protesting against the work of research laboratory Huntingdon Life Sciences (HLS), of which GlaxoSmithKline is a customer.

Police were called, but no action was taken.

A spokeswoman said the protest had not worried staff at the plant.

She said: "They are entitled to protest outside the plant and, to be honest, if someone really wants to break into a site, then they will manage it somehow.

"We won't be increasing our security, we will be carrying on as normal."

The break-in follows threats by Shac to demonstrate outside another of HLS's customers, chemical company Union Carbide.

It is understood that a protest was staged outside the home of a director of Union Carbide, in Marton, Middlesbrough, during the weekend.