Mass confusion over the United Kingdom's new Electronic Travel Authorisation (ETA) scheme and its impact on Australians with British ancestry has forced some Australian travellers to cancel trips abroad.

Dual Australian-British citizens must now travel on their UK passport to visit England, Scotland, Northern Ireland and Wales after the government updated its entry requirements.

The controversial new rules also means many Australians may unknowingly be a citizen of the UK if their parents were born in there or in a British territory.

Darwin couple Jessica and Steven Sangster's long-awaited family holiday to visit elderly parents in Scotland was ruined over this murky rule change.

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