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."
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."