Perth has been ranked the 21st most expensive city in the world, according to a global cost-of-living study.

Sydney and Melbourne are still among the top 10 most expensive, despite Australia falling down the costliness rankings in 2014.

The Economist Intelligence Unit's (EIU) Worldwide Cost of Living Survey, which compares 131 cities using New York as its baseline, ranked Sydney as the fifth and Melbourne the sixth most expensive on earth.

Price rises and a stronger currency resulted in Singapore claiming the dubious title of the world's most expensive city, followed by Paris, Oslo and Zurich.

The decline of the Australian dollar means that by the EIU ratings, Australian cities in 2014 offer better value for money to visitors.

Brisbane and Perth rank joint 21st, and Adelaide in 37th place offers the best value for money in Australasia, according to the study, which includes more than 400 individual prices.

That is because inflation and currency appreciation in neighbouring New Zealand mean Auckland (17th) and Wellington (19th) are more expensive than most Australian cities.

"The long-term rise of the Australian dollar, which has doubled in value in the last decade, has fallen back lately, with a corresponding decline in relative prices," report editor Jon Copestake said.

"But cities like Melbourne and Sydney now appear to have cemented their position among the most expensive across Europe and Asia."

The latest rankings have unseated Tokyo as the world's most expensive city, thanks to the declining value of the yen.

Asia and Australasia account for four of the 10 most expensive cities, as well as four of the cheapest.

Europe is home to half of the 10 most expensive cities, while New York has reclaimed its position as the most expensive city in North America thanks to declines in the Canadian city of Vancouver.

On the opposite scale, Mumbai in India is ranked the cheapest to live, alongside other South Asian cities such as New Delhi, Karachi in Pakistan and Kathmandu in Nepal.

A civil war and the collapse of the Syrian pound places Damascus among the world's cheapest cities.

THE TEN MOST EXPENSIVE CITIES IN THE WORLD

1. Singapore

2. Paris

3. Oslo

4. Zurich

5. Sydney

6. Venezuela

6. Geneva

6. Melbourne

6. Tokyo

10. Copenhagen



THE TEN LEAST EXPENSIVE CITIES IN THE WORLD

1. Mumbai

2. Karachi

3. New Delhi

4. Damascus

4. Kathmandu

6. Algiers

7. Bucharest

7. Panama City

9. Jeddah

10. Riyadh



THE MOST EXPENSIVE CITIES IN AUSTRALASIA

1. Singapore

5. Sydney

6. Melbourne

6. Tokyo

13. Hong Kong

14. Osaka

15. South Korea

17. Auckland

19. Wellington

21. Brisbane

21. Perth

21. Shanghai

30. Noumea

37. Adelaide



Source: The Economist Intelligence Unit, Worldwide Cost of Living study, 2014