As countries try to weaken their currencies to boost exports, the risk of a currency war similar to events seen in the 1930s has heightened, and policymakers are making sure they are on the winning side, according to Morgan Stanley.



The balance of power now rests with Japan, according to the bank, as Japan's policy-makers' more dovish approach looks set to bring the world a step closer to a currency war.



The Bank of Japan doubled its inflation target to 2 percent in January and made an open-ended commitment to continue buying assets from next year. This follows a leadership change, with new Prime Minister Shinzo Abe openly calling for aggressive monetary stimulus from the country's central bank.



(Read More: Land of the Falling Yen: Japan Cheers Sliding Currency)



This move, Morgan Stanley said, is a "game changer" as Japan tries to invigorate its stagnating economy .



"If a weaker yen is an important pillar of the strategy to make this export-oriented economy more competitive again, it brings into the picture something that was missing from earlier interactions among central banks of the advanced economies – competitive depreciation," it said in a research note.



"This, in turn, takes us one step closer to a currency war."