"The Fire Brigades Union (FBU) has joined Amnesty International in calling on the UK Government to press for a full international investigation into the devastating explosion in Beirut three months ago", the watchdog group said in a statement.
The organisation claims that the Lebanese authorities are not interested in conducting a transparent and impartial probe into what happened.
"The FBU and Amnesty are now urging UK Foreign Secretary Dominic Raab to support calls for a credible, international investigation. The investigation should be mandated to assess all aspects of responsibility for the explosion, said Amnesty and the FBU, making its findings public", Amnesty International added.
On 4 August, the Beirut port was devastated by a blast, which was believed to have been caused by the improper storage of ammonium nitrate. The explosions shattered the port and the city, killing at least 204 people, injuring many others, and knocking down or damaging houses and vehicles.