Speaking at a business forum on the sidelines of the Assocaition of Southeast Asian Nations annual summit, Najib said tariffs in the 10-member bloc averaged around 4.0 per cent in 2015.
However, non-tariff barriers and measures soared to 5,975 in 2015 from 1,634 in 2000, he said.
"This has to be checked and reversed," Najib told top business executives and entrepreneurs attending the forum.
ASEAN groups 10 countries with different political systems and varying levels of economic development from affluent Singapore to impoverished Laos.
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It has also signed free-trade deals with key trading partners such as Japan and China.
ASEAN's combined economy is expected to be worth USD 9.2 trillion by 2050, which would make it the fourth biggest economy in the world if it were a country, Najib said.
The bloc's collective economy was worth around USD 3.0 trillion in 2015, he said.
But Najib noted that for ASEAN to reach the 2050 target, non-tariff barriers must be trimmed by 50 per cent.