The Union Jack is not a national flag but a royal flag and its depiction can only be flown with royal permission.
It combines the red cross of St George (England), the Saltire Cross of St Andrew (Scotland) and the red diagonal cross of St Patrick (Ireland) - all Christian saints.
"The Union Jack signifies royal power and command based on Christian society and laws."
The top left position is known as the canton, regarded as the dominating and most important position as it is the highest and always visible even when the flag is limp (as in the stars in the United States' stars and stripes flag).
"The British Colonial Service adopted a 'one design fits all' policy with regard to most colonies and use three variations - British Blue Ensign for governance and state use, British Red Ensign for civil and governance use, British White Ensign for naval use," Mr Crawford said.
Some countries were allowed variations of the main colour - Fiji has a different blue, which represents the Pacific Ocean, and Canada had its own red until it changed it flag completely in 1965.
The blue for the British Blue Ensign came from the flag denoting the Queen as head of the Commonwealth and is commonly known as "royal blue".
"Each colony or dominion was asked to submit a specific variation which pertained to their land," Mr Crawford said.
"New Zealand's variation was only four white bordered stars which has been labelled as a 'highly stylised representation' of the Southern Cross.
"In all the descriptions and information about the Australian flag, they always make mention of The Southern Cross, while New Zealand's has to be described as a 'stylised representation' for accuracy as the fifth star is crucial to the Southern Cross' authenticity, both for nautical navigation and astronomical accuracy.
"Some say the four stars were chosen in sympathy to the four stars which appeared on a blue background on the original Maori flag in 1834, chosen by a selection of Maori chiefs and comprising two crosses with four stars.
"Whatever the origin, in 1902 the standard British Blue Ensign flag was changed to include the four stars and has been used ever since."
Most countries which were British colonies and have since gained independence have changed their flags and New Zealand and Australia are among the few still using the British Blue Ensign.
"Before they vote either way, everyone should ask themselves which flag best represents our fast-growing, multi-cultural, multi faith, multi-generational country, not only now but 100 years into the future.
"Ask themselves how do they want other nations to view our national flag as our national symbol, along with our kiwi, now and 100 years into the future."
-All information is contained in Complete Flags of the World, published by Dorling and Kindersley - www.dk.com