An attempt will be made at the High Court today to prevent a British company exporting a drug which could be used in the execution of US prisoners.
Solicitors representing two clients on Death Row and human rights group Reprieve are challenging Business Secretary Vince Cable's refusal to ban the overseas sale of sodium thiopental.
The strong painkiller is given as the first of a cocktail of three drugs used in US state lethal injections.
London-based solicitors firm Leigh Day & Co, acting for prisoners Edmund Zagorski and Ralph Baze, argue that Mr Cable's refusal was wrong in law.
Leigh Day says the case arises from the state execution in Arizona of Jeffrey Landrigan on October 25.
There was a delay in the execution caused by a shortage in the US of sodium thiopental.
A batch was obtained, and to assure the public of its quality the Attorney General of Arizona announced that it came from the UK.
On November 1, Mr Cable refused a Leigh Day request to use his powers under the Export Control Act to place an immediate ban on it being sold to the US for use in executions.
Mr Cable stated: "Sodium thiopental is a medicine. Its primary use is as an anaesthetic... Legitimate trade of medical value would be affected by any restriction on the export of this product from the UK."
Any ban would be ineffective, he added, because supplies could be obtained from elsewhere.
But anti-death penalty campaigners argue the refusal sits very uncomfortably with stated Government policy on actively seeking the abolition of the death penalty worldwide and, in particular, in the US.
Leigh Day's Richard Stein said: "Having failed to persuade Vince Cable that it is wrong for the UK to be facilitating the death penalty in the US, we hope that the High Court will now compel him to exercise the powers of export control which Parliament has granted him to prevent just this sort of violation of human rights.
"There is a list (of banned UK exports) which covers guillotines, gas chambers and electrocution equipment.
"We are simply asking Vince Cable to add sodium thiopental to this list."
Clive Stafford Smith, Reprieve's director, said recently: "US doctors have told us they do not use this drug (as an anaesthetic) any more.
"I would have thought that the British Government would do the right thing swiftly."