Britain on Monday vowed more reprisals against what it said was Tehran's "weakened and isolated regime" after it executed a UK-Iranian dual national.
Following the killing of Alireza Akbari on Saturday, the UK summoned Iran's most senior diplomat and recalled its own ambassador.
But despite slapping sanctions on Iran's prosecutor general Mohammad Jafar Montazeri it stopped short of opposition demands to ban the Iranian Revolutionary Guard Corps (IRGC).
Faced with more such demands in parliament, Foreign Secretary James Cleverly said he could not comment on future proscriptions.
He however said: "We do not limit ourselves to the steps that I have already announced."
Prime Minister Rishi Sunak's spokesman told reporters: "We are reviewing further action with our international partners."
British MPs voted last week in favor of adding the IRGC to a list of banned terrorist organizations in the UK.
But the government is wrestling with the fate of other dual nationals held by the Iranian regime, and with the strategic aim of restoring an international nuclear pact with Iran.
Cleverly was outspoken in denouncing Iran's leadership after Akbari, 61, was hanged allegedly for spying on Britain's behalf, AFP reported.
He told MPs that "we are witnessing the vengeful actions of a weakened and isolated regime, obsessed with suppressing its own people, debilitated by its own fear of losing power and wrecking its international reputation."
"Our message to that regime is clear: the world is watching you and you will be held to account, particularly by the brave Iranian people, so many of whom you are oppressing and killing."
British MP James Slaughter said he had "extensive contact for the past few difficult days" with Akbari's family.
"Earlier today I spoke to Mr. Akbari's daughter in the UK, and she asked me to raise a further distressing matter with the Foreign Secretary. The regime refuses to release Mr. Akbari's body or to allow burial in the place chosen by him, and have made threats to destroy his body unless the family co-operates with their instructions," he said.
Cleverly replied to Slaughter, saying: "The points that he just raised, I am sure, fill us all with revulsion.
"We will continue to support the family whatever way we can, and he is absolutely right to call upon the regime to treat Mr. Akbari in death with the deference and respect that is legitimate."
