Iran's foreign ministry warned the UK on Tuesday that giving diplomatic protection to a British-Iranian mother jailed in Tehran would not make the situation "easier", state news agency IRNA reported.
Britain on Friday extended the status to Nazanin Zaghari-Ratcliffe, who was arrested in Tehran in 2016.
"What is certain is that the British government's move lacks goodwill and is in no way constructive or positive," said ministry spokesman Bahram Ghasemi on Tuesday.
"If it does not make the situation more complicated, it will surely not make things easier."
Zaghari-Ratcliffe, who worked for the Thomson Reuters Foundation -- the media organisation's philanthropic arm -- is serving a five-year jail sentence for sedition.
She has denied all the charges against her.
Diplomatic protection is a rarely-used mechanism allowing governments to seek protection for their citizens on the grounds that they have been wronged by another state.
Britain's Foreign Secretary Jeremy Hunt said Friday that London would take the "extremely unusual" step of extending diplomatic protection to the jailed mother.
This would signify the "formal recognition by the British government that her treatment fails to meet Iran's obligations under international law", he said.
But Ghasemi denied this, saying Zaghari-Ratcliffe is "enjoying all legal and citizenship rights -- both throughout her trial proceedings and during the conviction period", including medical care.
Tehran was informed of the UK's decision via official channels, and is currently studying the legal and political implications, the spokesman said.
Ghasemi dismissed the move as "merely reflecting a political decision by the UK" and said that it would not "in itself bring about a new legal status internally or internationally."
Iran's envoy to London said last week that the UK's decision "contravenes international law", as governments can only exercise such protection for their own nationals.
Writing on Twitter, Hamid Baeidinejad said Iran does not recognise dual nationality.
"Irrespective of UK residency, MS Zaghari thus remains Iranian," he wrote.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)