The British government said it was putting additional export controls on the export of pancuronium bromide, potassium chloride and sodium pentobarbital.
Last year, the London-based human rights group Reprieve sued the British government to stop it exporting another drug, sodium thiopental, a sedative legally required for U.S. lethal injections, which was in short supply in the United States.
That led to Britain, which opposes the death penalty, imposing an emergency export ban on the drug.
"We oppose the death penalty in all circumstances and are clear that British drugs should not be used to carry out lethal injections," Business Secretary Vince Cable said in a statement.
"That is why we introduced a control on sodium thiopental last year -- the first of its kind in the world. And it is also why we are now controlling the export of the other drugs used in lethal injections in the U.S."
In December, the Death Penalty Information Center said the United States had executed far fewer people in 2010 than in previous years, partly because of a shortage of sodium thiopental.
The Department for Business said it had consulted the British suppliers of the drugs and other interested parties and concluded legitimate medical trade would not be affected.
It said measures to ban exports of the drugs would go before parliament in the next few days and would take effect the following day.
Cable said he was urging other European countries to follow Britain's lead in order for the control to be effective.
"Since the U.S. executing states are now turning to a Danish company, Lundbeck, to kill people, we must hope that the UK can persuade our EU partners to take a similar line," Reprieve Director Clive Stafford Smith said in a statement.
In February, drugs company Novartis said it had taken steps to prevent a generic version of sodium thiopental reaching the United States. (Reuters)
