Asked about a sit-in that Zaghari's husband has staged in front of Iran's Embassy in London, Abbas Mousavi told reporters at a press conference on Monday that making decisions about security convicts comes within the purview of the country's Judiciary.
Iran views Zaghari as an Iranian national who has committed security crimes, the spokesman added, stressing that such acts of blackmail in London would not really work.
Iran is opposed to any disturbance hampering its embassy's normal activities in London, the spokesman said, adding that such disruptive protests run counter to international conventions.
Any protest needs to be addressed through legal approaches, so that the Iranian Embassy could do its normal activities, Mousavi concluded.
Last week, Iran's ambassador to the UK expressed dissatisfaction with a protest blocking the only entrance of Iran's Embassy in London and restraining Iranian diplomats from entering into the building.
The husband of Zaghari has staged a sit-in outside the Iranian Embassy in an apparent attempt to secure the release of his wife.
At the time of her arrest in April 2016, the Islamic Revolution Guards Corps (IRGC) referred to Zaghari as "a main ringleader of hostile institutions who had been involved in criminal activities over the past years under the auspices of the foreign governments' media and espionage services."
She is now serving a five-year sentence in Iran.