Capital punishment is a serious human rights violation and the UK should be opposing its use in every instance, not just when it suits it politically.
Human rights campaigners have called on the government to reaffirm its opposition to the death penalty as they accused the UK of showing a "new flexibility" in its approach to capital punishment.
Amnesty International's call comes after Home Secretary Sajid Javid faced criticism in July last year after not seeking assurances that Alexanda Kotey and El Shafee Elsheikh, two of the so-called Isis Beatles, would not face execution if they were extradited to the US.
The charity's annual report on the death penalty globally showed an increase in capital punishment in nations which are UK international allies such as the US and Japan, despite executions overall falling by nearly a third last year.
Kate Allen, Amnesty International UK's director, said: "Historically, the UK has a good record in terms of encouraging other countries to abolish the death penalty, but last year's backtracking in the case of Alexanda Kotey and El Shafee Elsheikh was extremely worrying.
"Kotey and Elsheikh's alleged crimes were appalling, but that doesn't justify the UK in adopting a pick-and-mix attitude in its opposition to the death penalty. You either oppose the cruelty of the death penalty, or you don't."
The pair are accused of belonging to a brutal four-man cell of Islamic State executioners in Syria, nicknamed The Beatles because of their British accents, responsible for killing a number of high-profile Western hostages.
They were captured in January last year, sparking a row over whether they should be returned to the UK for trial or face justice in another jurisdiction.
Ms Allen added: "One of the likely fall-outs from the UK's new 'flexibility' on the death penalty is the possibility that pro-death penalty governments will begin to accuse the UK of hypocrisy if we oppose their use of capital punishment.
"Capital punishment is a serious human rights violation and the UK should be opposing its use in every instance, not just when it suits it politically."
The report revealed that globally the number of executions in 2018 fell by nearly a third to 690, the lowest in a decade. But this also saw a rise in executions in countries including Iraq, Egypt, Japan, Singapore, South Sudan and the United States.
China is believed to be the world's most prolific executioner, where thousands are believed to be put to death each year, however that data is still classified as a state secret.
Despite a significant decrease in the numbers from Iran, the figures showed the nation still accounted for more than a third of the known executions recorded globally last year.
Kumi Naidoo, Amnesty International's secretary general, said: "Japan, Singapore and South Sudan reported their highest levels of executions in years, and Thailand resumed executions after almost a decade - but these countries now form a dwindling minority.
"To all the countries that still resort to the death penalty, I challenge you to act boldly and put a stop to this abhorrent punishment now."
Mason Boycott-Owen is a journalist with the Press Association.