BRITISH efforts to halt the sale of lethal-injection drugs to the US have been seized on by American death-penalty supporters.

They are calling for the method to be scrapped in favour of firing squads or a return to the gas chamber.

Within hours of a British export ban on sodium thiopental and other drugs coming into force on Friday, a leading death-penalty advocate in California said that a modernised gas chamber was “the obvious solution” to a backlog of more than 700 death-row inmates whose fate depended on state approval of a new method of execution.

In New York, a prominent law professor who favours execution as “retributive” justice called for a return to the widespread use of firing squads as a form of capital punishment that “doesn’t pretend to be something else”.

International pressure on suppliers of the three drugs most commonly used for lethal injections over the past three decades — sodium thiopental, pancuronium bromide and potassium chloride — has led to a shortage of the drugs in the US and an urgent push by state governments for alternatives.

Only two states have switched to a new drug protocol, leaving 32 others using up supplies or in transition to a new regime, while nearly 3000 death-row cases nationwide languish in legal limbo.

In California, the future of the death penalty will be decided by a judge, who must rule on the legality of a new drug cocktail in which a barbiturate often used for putting down animals could be substituted for sodium thiopental.

However, as judge Jeremy Fogel deliberates, Kent Scheidegger, of the Criminal Justice Legal Foundation, has offered an alternative: a modernised gas chamber in which cyanide gas is replaced with a neutral gas such as helium.

The effect on a prisoner would be similar to that of hypoxia on a pilot suffering oxygen deprivation at high altitude, Mr Scheidegger said. “It feels like nothing. You just feel kind of woozy,” he added. “For anyone thinking longer-term about alternatives to lethal injection, this is the obvious solution.”

He blamed a failure to think seriously about a modernised gas chamber on bureaucratic inertia. The method is widely seen as unacceptable because of its echoes of the Holocaust, but Mr Scheidegger wrote recently: “We used the gas chamber when World War II was still fresh in people’s minds, and gas as such was not a problem then. It should be less of a problem as that era fades from history.”

New York Law School professor Robert Blecker said lethal injection should be abandoned — not for practical reasons, but because it sanitised a process that should hurt. “It conflates medicine with punishment,” he said. “How we kill those we detest should in no way resemble how we kill those we love.

“Firing squad is my preferred method,” he said.