The British Foreign Office warned that British and Iranian-British citizens are significantly at risk of arbitrary detention if they travel to Iran.
The Foreign, Commonwealth and Development Office (FCDO) in a notice on Thursday advised British nationals against all travel to Iran.
It warned that the British passport can make Iranian authorities target travelers and they could spend months or years behind bars.
“Our ability to provide consular assistance is extremely limited. In an emergency – such as serious deterioration in the security situation – it is extremely unlikely the British government will be able to evacuate you or provide assistance on the ground in Iran,” reads the notice.
It also cautioned the British nationals, who are already resident in Iran, that they should carefully consider their presence and the risks they are taking by remaining.
There have been several high profile cases of British-Iranian dual nationals being arbitrarily detained in Iran and forced to serve long prison sentences as part of the country's strategy of hostage diplomacy.
“The criminal justice process followed in such cases falls below international standards. If you are detained in Iran your case will be in the hands of the Iranian authorities, who have shown a pattern of hostility towards the UK and its citizens,” added the Foreign Office.
The Iranian authorities have accused people with links to the UK of inciting protests, the Foreign Office warned saying that if the nationals are in or near a protest, they are at serious risk of arrest.
“Anyone who is arrested in connection with protests and holds British nationality may come under added suspicion of espionage or working to undermine the Iranian government.”