The people of Scotland will go to the polls in September next year to determine whether the country should achieve independence from the United Kingdom.

As the blue in the Union Jack represents the Scottish national flag (the Saltire, or flag of St Andrew), there has already been debate in Britain about whether the flag would need to be amended should the Scots choose to go it alone.

The make-up of the Australian national flag is defined in the Flags Act of 1953, which includes ''the Union Jack occupying the upper quarter next the staff''.

So would a change in the Union Jack have a flow-on effect in the antipodes?

University of Queensland constitutional law expert Graeme Orr said although there could be a legal argument made for change, it was unlikely to have a serious chance of success.

''Because our act has the visual reference to make it clear what our flag looks like, plus the rule of statute interpretation is that you go looking for the meaning, including what was intended at the time, it's pretty clear at the time it was a particular Union Jack,'' he said.

''It may have been different 90 years ago. You might have said maybe there's an argument that what they intended was we were always going to be tied to Britain, but that's all evolved.''

A spokesman for the honours, symbols and territories branch of the Department of the Prime Minister and Cabinet said the Scottish referendum could not change the national flag.

''The Flags Act 1953 [Section 3(2)] requires a poll of all Australians before the design of the Australian national flag can be changed,'' the spokesman said.

But Professor Orr said the flag could quite easily be changed by Parliament, despite the referendum clause that was introduced by the Howard government.

''One parliament can't say to a future parliament 'we're going to bind you to a referendum' - a later parliament could just undo that,'' he said.

Vexillologist Ralph Kelly said even if legal impediments were overcome, the basis of the argument against change was that the current flag represented the nation's history and the British contribution to Australian laws, democracy, language, values and traditions.

''These British elements would not change if Scotland and England divorced,'' he said.

Mr Kelly said it was entirely possible Britain would maintain the current Union Jack due to its history, even in the event of Scottish independence.

''This approach was taken by the Czech Republic when Slovakia separated in 1993 - it continued to use the flag of Czechoslovakia, even though the blue part of the flag had historically represented the Slovak region,'' he said. ''In my opinion, this is the most likely option for the British government.''