The United Kingdom's ambassador to Iran has been described as "persona non grata" by Iran's judiciary spokesperson who called for his expulsion from the country.

UK envoy Rob Macaire was briefly detained on Saturday night after he left a vigil held for the 176 victims of a plane crash caused by Iranian missiles.

"Under international law, such a person is a 'persona non grata,'" judiciary spokesman Gholam Hossein Esmeili told reporters in Tehran on Tuesday.

He added that "the [Iranian] people expect the person to be expelled" according to international norms.

According to a security source quoted by Iran's state media, Macaire was trying to "provoke and organize" an anti-government protest in front of Amir Kabir University in Tehran.

Macaire rejected all accusations and insisted he left the gathering as soon as a group started to chant.

Thanks for the many goodwill messages. Can confirm I wasn't taking part in any demonstrations! Went to an event advertised as a vigil for victims of #PS752 tragedy. Normal to want to pay respects- some of victims were British. I left after 5 mins, when some started chanting. — Rob Macaire (@HMATehran) January 12, 2020

The judiciary also accused the diplomat of "interfering in Iran's internal affairs".

Photos circulating on social media showed banners with Macaire's face were set on fire on Tuesday.

Diplomatic spat between Iran & UK continues after British ambassador was briefly detained at a protest. Judiciary spox says he didn't respect intl. law & should be expelled, as he is 'persona non grata' in #Iran. Hardliners burn effigy of ambassador along with US & UK flags. pic.twitter.com/WwFdLZBogi — Ali Arouzi (@aliarouzi) January 14, 2020

The labelling of Macaire by the judiciary spokesperson as "persona non grata" is not legally binding, and the final decision over the diplomat's expulsion would be taken by Iran's foreign ministry.

Gatherings to commemorate the victims of the Ukrainian flight crash turned into protests across Iran following the Islamic Revolutionary Guard Corps' (IRGC) admission on January 11 of having mistakenly shot down the passenger jet after initially having denied doing so.

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The diplomatic spat between the UK and Iran has added to rising tension between the two countries.

On Tuesday, British Prime Minister Boris Johnson reiterated his willingness to work on a "Trump deal" to replace the international accord agreed between Iran, the five permanent members of the UN Security Council, and Germany.

Johnson's comments came after the UK, France and Germany decided to trigger the deal's Dispute Resolution Mechanism which brings a potential collapse of the accord closer and eventually, the re-imposition of United Nations sanctions.

The European powers' move is the strongest response yet to Tehran's steps away from the unravelling pact. Since President Donald Trump's decision to withdraw the US from the nuclear deal in May 2018, Iran began dropping its commitments under the accord formally known as the JCPOA.

According to the three European powers, the dispute mechanism is "a solution for the return to full compliance" to the nuclear deal that was signed in 2015 to curb Iran's nuclear power in exchange to sanctions relief.