The register of members' interests reveals Fine Gael justice spokesman Jim O'Keeffe, fellow Cork TD Ned O'Keeffe and Ceann Comhairle Rory O'Hanlon hold shares in GSK, which has a manufacturing facility in Cork and sales and marketing business in Ireland. TDs with less than 13,000 shares are not required to disclose holdings.

A group called Campaign Against Huntington Life Sciences has begun writing to GSK shareholders, and has threatened to write to all 167,000 private shareholders. The campaigners want GSK to stop working with Huntington, which uses animals for drug tests.

The letter advises shareholders if they do not sell their shares within 14 days "your details will be publicised and within weeks a website will be hosted with all remaining shareholders listed". GSK has obtained an English high court ruling banning the group from writing to its shareholders, but this is not enforceable in Ireland.

"Any campaign of intimidation is disgraceful and to be utterly condemned, " said Jim O'Keeffe, who said he has not received a letter and does not know whether he holds his shares in a nominee account.

"I'm quite prepared to discuss people's concerns in a rational, civilised manner if they present them in a rational, civilised way, " he said. "I would be supportive of any reasonable move to ensure animal experiments are being carried out in a humane way."

Ned O'Keeffe hasn't received a letter either. "I'll definitely receive one after this phone call, " he said. He has no problem with being a shareholder in GSK, he said.

"They do a good job for animal health and human health. You have to have people who research, if they don't they'll put the human race at risk."

Rory O'Hanlon declined to be drawn. "As ceann comhairle, he doesn't feel it is his position to comment in any way, " a spokesman said.