NEARLY ALL FORMER BRITISH COLONIES REMOVED THE UNION JACK FROM THEIR FLAG WHEN BRITAIN WANTED TO JOIN THE EEC

​NZ FLAG FACT NUMBER 30 

Fifty-three independent nations belong to the British Commonwealth. Four of these countries have never had the Union Jack on their flag, forty-four have removed the Union Jack from their flags, and Fiji is in the process of changing its flag, which will take the number to forty-five. No former British colony from Africa, Asia, the Caribbean or the Americas has the Union Jack on their flag any longer. 

The vast majority of British Commonwealth countries changed their flag during the 1960s when Britain attempted to join the EEC in order to secure trade benefits (France twice blocked Britain’s efforts in this regard).

​In 1973 the EEC finally accepted Britain as a member, after which New Zealand exports to the United Kingdom dropped dramatically. ‘There was no shadow of a doubt that the British application of 1961 [to join the EEC] presented a threat to New Zealand trade of the gravest dimensions. Prime Minister Holyoake summed it up when he said that the bid to join “raises questions probably the most serious New Zealand has had to face in times of peace”.

However, despite calls from various New Zealanders to have the Union Jack erased from the New Zealand flag, this symbol has continued to feature on it. The only other independent Commonwealth Countries that still have the Union Jack on their national flags are Australia and Tuvalu, which, like New Zealand, are countries located in the Pacific Ocean.
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From New Zealand Flag Facts by historian Malcolm Mulholland. Read more at: ​
http://www.silverfernflag.org/press/new-zealand-flag-facts-book