Rasoul Movahedian-Attar is expected to take up the post which has been vacant since late 2005 when hard-line President Mahmoud Ahmadinejad recalled 40 of the countrys ambassadors and envoys as part of a purge of the Islamic Republics diplomats who did not belong to the ultra-Islamist faction.
In April, Iran Focus reported that a number of officials appointed by Ahmadinejads government for the posts of Irans ambassadors to European countries had been rejected by the host countries.
The Iranian Foreign Ministry has since been struggling to find replacement candidates.
Movahedian-Attar was previously Tehrans top envoy to the Czech Republic, Slovakia, and Portugal.
London has not formally commented on the appointment.