Representatives from seven states - including Argentina, The Bahamas, The Czech Republic, Portugal, Senegal, St Lucia and Uruguay - will deposit their ratifications.

The move triggers a 90-day countdown to the Treaty becoming international law on December 24, 2014 - only 18 months after it first opened for signature, in June 2013.

David Grimason said: "Today marks a crucial step in bringing the Arms Trade Treaty into force. The fact that 50 states have ratified it so quickly shows just how important this Treaty is and just 90 days from today it will become international law.

"For me, this journey has been a highly personal one, my son was killed by a man with an illegal gun and everyone who loved him has suffered a terrible loss. "Today brings hope that other families won't have to experience that pain."

Georgia and Namibia will also sign the Treaty - the step prior to ratification - , taking the total number of countries who have signed to 121 so far.The ATT is the first global agreement to regulate the $85bn annual trade in arms and ammunition. Figures released by the UN's refugee agency UNHCR in June showed 33m people fled armed violence in the previous 12 months.

Director of the Control Arms Coalition Anna Macdonald said: "The ATT will enshrine into international law much-needed controls on the multi-billion-dollar arms trade for the first time.

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