A third American prisoner died in agony after an anaesthetic supplied by a British company failed to work properly, it has been claimed.
Dream Pharma, a small company run from the back of the Elgone Driving Agency in Horn Lane, Acton, west London, is understood to have supplied the anaesthetic sodium thiopental used in the US executions of Emmanuel Hammond, Brandon Rhode and Jeffrey Landrigan.
A claim has now emerged that Landrigan, a convicted murderer, kept his eyes open after receiving a lethal injection - an apparent sign that the anaesthetic had not worked.
Dale Baich, a lawyer who witnessed the execution in Arizona last October, made the disclosure in a sworn statement for legal action charity Reprieve's pending High Court action.
Reprieve claims the other two prisoners also kept their eyes open and has written a letter to the Medicines and Healthcare Products Regulatory Authority (MHRA) asking them to recall all of Dream Pharma's sodium thiopental.
The charity said that if the MHRA does not respond by the end of Monday, they will file action against them in the High Court the following day.
Reprieve investigator Maya Foa said: "Why does a regulator exist if not to prevent British drugs failing or, worse, causing pain to patients?
"It is difficult to see how much more evidence the MHRA needs in order to recall a faulty drug. If Dream Pharma's sodium thiopental is not taken out of circulation, more prisoners are likely to die in agony and the MHRA will bear responsibility for their ordeal."
Business Secretary Vince Cable banned the export of sodium thiopental in late November after the drugs used to execute the three prisoners had already been shipped to the US.