Hong Kong is now the most expensive city in Asia for ex-pats and the third most costly in the world, with Singapore right behind in fourth place globally.

For the second year running the two most expensive places to set up in as an ex-pat are African cities, according to a survey by Mercer, designed to help multinational companies and governments set the size of compensation allowances for their expatriate employees.

Hong Kong leapfrogged from sixth to third place; Singapore gained one spot from 2013 to stand fourth.

Tokyo, hitherto Asia's most expensive city for expats, dropped four places to seventh. Shanghai stood 10th on the list, jumping four spots from 2013.

Four of the top 10 cities in 2014's rankings are in Asia.

London is ranked as the 12th most expensive city for expats to live in, having shot up 13 places from 25th in 2013.

Birmingham is the UK's second most expensive city and is ranked this year in 90th place, up from 135th.

Aberdeen, with its strong oil industry, has moved up the ranking to become the 94th most expensive city, while Glasgow is at number 108. The Scottish cities have jumped 34 and 49 places up the rankings respectively since last year.

"This year, UK cities have surged in the ranking, mainly as a result of a strengthening of the pound against the dollar," said Ellyn Karetnick, UK head of Mercer's International Mobility Practice

Ed Hannibal, Partner and Global Leader for Mercer's Mobility practice, said in a statement: "Rankings in many regions were affected by recent world events, including economic and political upheavals, which resulted in currency fluctuations, cost inflation for goods and services, and volatility in accommodation prices."

"While Luanda and N'Djamena are relatively inexpensive cities, they are quite costly for expatriates since imported goods come at a premium. In addition, finding secure living accommodations that meet the standards of expatriates can be challenging and quite costly as well," Hannibal added.

PwC Poll

London is the top city of opportunity, beating New York by a "good margin" and Singapore, according to a recent PricewaterhouseCoopers (PwC) survey.

The survey's results, released May 2014, revealed that London finished first in "technology readiness, economic clout, and city gateway" which proves its place as a thriving economic powerhouse.

New York "continues to show strong consistency across most of the categories", despite not finishing top of any of the criteria, which also included transportation & infrastructure, ease of doing business, cost, and demographics & liveability.

The Big Apple, however, finished in second place edging out Singapore, which jumped up four places, according to PwC.

The figures for Mercer's cost of living and rental accommodation costs comparisons were derived from a March 2014 survey. Exchange rates from that time and Mercer's international basket of goods and services were used as base measurements.